The article makes a good point: JPEG XL is amazing but not specifically for the typical Web use cases, compared to AVIF. But the conclusion doesn't follow. Having an excellent and versatile format supported by browsers is very useful!
Maybe a lossless re-encoding of my website JPEGs to gain 20% size is not worth the 33% longer decode, and maybe the website doesn't need very high resolution images or more than 12 bits per channel. But my personal archives can definitely use that and it's great that such files can be viewed everywhere without specialized tooling, including served on the intranet and indeed the Web.
In summary JPEG XL easily beats AVIF on the not-so-long tail of use cases and having compatible viewers everywhere is quite useful. And with JPEG XL becoming part of PDF, it will soon be common use cases too.
As for the rest of the article: there are interesting points in the benchmark section but I think it's too early in the JPEG XL adoption cycle to draw conclusions. One thing bothers me though: There is a single picture comparison (with tag line "results speak for themselves") and I find it quite misleading: it's just picking one point on the "bytes received" line that looks best for AVIF compared to JPEG XL. Try it yourself and you'll see JPEG XL shows something already at 2KB while AVIF has nothing until 8KB, and JPEG XL looks better than AVIF after 100KB.
+1, this is super unfair to show the one point in time where AVIF progressive looks better - right after it receives its 'preview' (which as you say is 4x as big as JPEG XL's).
I value integrity, especially when communicating results. This is shameful.
“For progressive, I think it's better to show the user something that's obviously a preview, but still has enough detail to be able to know what the picture is of.
If you're showing the user something that they may mistake for complete but poor quality, that's a bad experience.”
For progressive, I think it's better to show the user something that's obviously a preview, but still has enough detail to be able to know what the picture is of.
If you're showing the user something that they may mistake for complete but poor quality, that's a bad experience.
Depends on the user. Some users are more sensitive for flashing images. Some users have very slow or unreliable network connection. Some sites have bigger images. Some sites (such as ecommerce) have higher quality and resolution needs.
Some users have uncorrected astigmatism. In the general population, the average uncorrected astigmatism typically falls between 0.50 and 0.75 diopters (D), and ~15 % more than 1.0. The high astigmatism people will see images blurred in any case and don't benefit from the fine structural detail JPEG XL can give. People with glasses and the lucky ones with low astigmatism will see the details clearly.
Sometimes passionate ends of different quality of vision seem to have a discussion on what makes sense as the web quality, with one emphasizing quality 40 being more than enough and another requesting a quality of 95.
The same kind of individualism exist also in temporal cognition and perception.
The quality of the preview layer is somewhat under the control of the user though.
And that comparison was made for a JPEG-XL focused site, and uses quite large images that are then scaled down dramatically (at least on mobile) for display which is probably not an ideal visual test anyway (but possibly necessary for there to be enough time to see any difference)
Agreed. Browsers should support general-purpose image formats. I'm not interested in another “web codec” that's not good for anything but passive delivery.
> Maybe re-encoding my website JPEGs to gain 20% size is not worth the 33% longer decode
I changed all my .jpg files to .avif a few years ago. The benefit I get is much more than 20%. Now there is some loss when I use high compression with .avif, in particular via gimp - but other than that, I gained a lot of file size here, definitely much more than 20%. It also depends on the image at hand; I noticed that images with a ton of details, such as if you photograph a garden, takes more space. But for simpler images, I have easily gains of about 60% or 70% compared to jpeg, with no or almost no loss in quality. Whereas if I were to use jpeg compression, the quality loss would be insanely high. When I noticed this, I decided to abandon .jpg for my own use cases. I had to choose back then between avif and webp and while webp is fine, I found .avif was slightly better for the use cases I had.
I don't quite know how much jpeg xl performs, but you mentioned JPEG so I had to comment on that 20% statement as I found it way too low.
I also find the claim "longer decode" not correct. I have some photographs of gardens and the file size is huge, in JPG. When I compressed and changed these into .avif, the resulting page loads soooooooo much faster now when having used avif and a considerable but acceptable compression of it. It is just no comparison at all - avif beats jpg with its eyes closed.
Sorry if that was confusing, I have edited my post to clarify a bit: That sentence was about a feature specific to JPEG XL, which is that if you have JPEG files you can re-encode then as JPEG XL to save space without any loss of quality. It's nice for peace of mind, you can bulk convert a large archive and you know you still have the same pixels everywhere (later you can even turn them back to JPEG without loss if you want). AVIF cannot do that. Now if you are OK with some loss in the conversion, you can also do much better than 20% with JPEG XL.
It sounds like you lossily re-encoded lossy JPEGs to AVIF, am I reading that right? If so, you're automatically suffering from generational loss there, it can't be the basis of any coherent argument.
The entire article is extremely cherry picked, and it's notably that there are a couple of people leaving dozens of comments in here each (which is odd as normally HN gates that sort of gross overrepresentation). Like >10% of comments in this 300+ comment discussion is one single person, endlessly changing positions based upon what makes JXL worst.
It's bizarre. I've never seen a format see such ridiculous attacks.
>Maybe a lossless re-encoding of my website JPEGs to gain 20% size is not worth the 33%
I was unpleasantly surprised when jxl's reference encoder dropped critical exif tags for no reason whatsoever from my personal archives. Turns out their lossless preset wasn't really lossless.
And then webp to JXL conversion also produced different viewing experience results as ffmpeg's webp decoder wasn't handling ICC correctly.
I'm now very cautious of any "lossless" re-encodes.
> Maybe a lossless re-encoding of my website JPEGs to gain 20% size is not worth the 33% longer decode,
And pray tell how much of the waiting for page is used on decoding image (vs transferring) and how much faster the image gets on the machine when it's 20% smaller on average connection?
My guess is that time saving from bandwidth decrease more than compensates for that
A potentially major issue I have with AVIF is that because it is based on a video format, any hardware decoding support AVIF will get is likely to be restrained to common video scenarios. This can result in eg. only 4:2:0 YUV being supported by hardware decoders, as that's the upper limit of AV1 Main Profile (and thus the limit of AVIF Baseline Profile). And 4:2:0 is just a poor fit for certain categories of images (like various kinds of illustrations, screenshots, etc). I would not be very happy about a web where lossy 4:4:4 image compression would be heavily discouraged with modern formats.
Also, good lossless compression absolutely does matter for the web as well. Lossy images just cannot be used in all circumstances - like when comparing compression quality (especially of videos), for example!
EDIT: To give an additional example, pixel art is an entire field of art (which is very much still active today) where both lossless compression is a must and where 4:2:0 would be absolutely catastrophic for quality.
> And 4:2:0 is just a poor fit for certain categories of images (like various kinds of illustrations, screenshots, etc).
I'd go even further and say that 4:2:0 is unsuitable for still images, period. Even for cases where it would be a suitable tradeoff for video. And even for video there's a significant chunk of content where it's undesirable.
In general I think we've come to accept some pretty gnarly limitations on image quality that really should not be such a given. 8 bits per channel is another one. You actually really do notice the banding with the naked eye in a fairly large range of situations, and if everything is 8 bits per channel then it gets really easy to exacerbate the problem on edit. Dithering in 8 bits per channel isn't really a solution because it's hard to do and it gets lost in compression quickly.
4:2:0 is the main reason why most games look like crud once they've passed through any mainstream video encoding pipeline. That being said, the bitrates used for streaming games and VoDs are so low everything looks like mush anyway and millions still watch that.
Browsers already fully support 4:4:4 AVIF and are not going to regress on this, as it would be a huge compat issue.
It isn't clear whether AVIF hardware decoding will ever be an advantage, but for video formats, Firefox and Chrome already pick between hardware and software decoders to ensure the content plays correctly. Safari is much flakier here, but again, for images, they're not going to regress on 4:4:4 AVIF support.
Lossless AVIF encoding is inferior to JXL though, the article oddly dismisses lossless as a valid case for the web so it ignores the core argument that lossless is critical for some type of content.
I find the hardware support argument far more compelling that diminishing the value of lossless publishing.
There have been a number of experiments to use hardware decoders for images in browsers, all of which have fallen flat; not even Safari does it for AVIF or WebP. Thus, 4:4:4 AVIF is supported absolutely everywhere. Feel free to try it now. I can see how hwdec is compelling for JPEG XL in theory, given how slow decoding is.
In the modern age image decoders need to handle untrusted inputs, and the big players rarely use hardware image decoding, even when it's available, because it's so hard to rely on its memory safety.
Several 'zero click exploits' have involved image/document format decoder bugs, as messaging apps and file browsers will often generate preview images the moment an image arrives.
Yes, I know the format supports it. The question is, will hardware decoders built primarily around video use cases? And if those kind of hardware decoders end up forming the majority of hardware decoders for AVIF, will we end up in a future where using the full range of the format is heavily discouraged because it won't be supported by hardware decoders?
For comparison, it was possible to do 10-bit video with H.264, but 10-bit video didn't see any mainstream adoption with it because hardware decoders generally didn't support 10-bit H.264 video. Only when newer formats came around and specced 10-bit support as a baseline necessity did we start to see wider adoption for it. And well, the baseline specs (main profile) for AV1, which AVIF is based on, are limited to 4:2:0...
I'm not super familiar with AV1/AVIF but I do have extensive experience using h264 for desktop streaming, and all major implementations support 444 in hardware and software, and I doubt more advanced codecs/image formats have a limitation like this. Asked ChatGPT and it also claimed there's no problem with 444 and AVIF/AV1.
> I'm not super familiar with AV1/AVIF but I do have extensive experience using h264 for desktop streaming, and all major implementations support 444 in hardware and software, and I doubt more advanced codecs/image formats have a limitation like this.
This is a good helpful comment containing relevant information from personal experience.
> Asked ChatGPT and it also claimed there's no problem with 444 and AVIF/AV1.
This part is useless, there's no one who cares what a LLM thinks that can't just prompt it themselves.
Then chatgpt missed an obvious issue, nvidia definitely have had shortcomings in the hardware implementation of coder/decoders only supporting 420 in nvenc/nvdec. One obvious problem with that was that it affected premiere.
Strange blog post. Given that it's from a developer of proprietary and paid commercial encoders, the inclusion of their upcoming "aperture-alpha" encoder on the charts that are purportedly about JPEG XL makes this feel like a marketing piece of some fashion. Certainly, they advertise their Iris-WebP encoder throughout the post, with an implication that if you haven't paid to the author for it, you're not using WebP correctly, I guess?
Moreover, there are some methodological oddities. For example, JPEG XL decoding is tested in single-threaded mode when it's optimized for multi-threaded decoding (where AVIF has artifacts from tiling). Also, the tested command is "jxl_cli --speedtest", which means that the benchmarked time includes the warm-up procedure of the "--speedtest" flag, rather than the pure decoding time.
Another example of this is progressive rendering, where the comparison moment is chosen at a local maximum that favors AVIF. JPEG XL materializes a full frame much sooner than AVIF, and starting at, say, the 96,256 B mark, it looks better than AVIF until the full image is loaded.
I expected one of these bad-faith readings, so I can address that Aperture is mentioned once and Iris-WebP is only shown in numbers, because I have access to these encoders and thus they cannot be ignored. The only encoders I heavily advertise here are the incredible open-source AV1 encoders, that I contributed to for free and I think people should use. Also, not sure where you infer that point about WebP; libwebp is a fine encoder.
AVIF does not have artifacts from tiling any more than JPEG XL has artifacts from being JPEG XL; if you read the details post at the bottom, you'd see there's a 0.5-1.0% BD-rate regression with tiles, which is effectively a rounding error.
For progressive, JXL shows a blurry mess for the majority of its decode, while AVIF shows a crisp image that clearly shows what is in the image. Go ahead and try the demo yourself! AVIF also supports more than one layer, but I used Team JXL's image on purpose to show that even there, AVIF looks better for 90% of the decode time. You need to watch what I'm showing you instead of adopting the most bad-faith reading because some things are mentioned.
> For progressive, JXL shows a blurry mess for the majority of its decode, while AVIF shows a crisp image that clearly shows what is in the image. Go ahead and try the demo yourself! AVIF also supports more than one layer, but I used Team JXL's image on purpose to show that even there, AVIF looks better for 90% of the decode time.
I'm not sure I agree? IMO after about 30% most images look better on JXL than on AVIF, the exceptions being the pigeon, which looks better on JXL after 43% (still less than half) and the sunflower, which looks better on 66% (but you can clearly see what's on the image a lot earlier). Also, blurry convey better the idea of loading and the AVIF version may have some weird artifacts / look weirder (although that's subjective), for example the Quechua woman's eyes are very distorted on the progressive AVIF and, on the Poke bowl, some of the seeds on top of one of the top radish pieces are kind of missing / look like a shadow (while other seeds of the same size appear). In contrast the JXL version is usually blurrier and less saturated at the beginning but is more "uniform/reliable" (distorts all of the "objects" more or less the same), and later it looks finished but actually isn't (which may be a problem on its own).
Hi there! I'm Julio (co-developer of libaom and SVT-AV1's tune IQ). Here there are some points worth mentioning, because I'm catching a whiff of bad faith with your comment that honestly needs to be called out:
- The inclusion of his two proprietary encoders (Aperture and Iris) just serves to further support the argument that JXL encoder devs have work to do to perform at the frontier, while also proving you only need a person or two to do so. The two FOSS AV1 encoders in the compo (libaom and SVT-AV1) are enough to prove this. Given that blog posts often double up as a way to show-case projects, I think it's fair game to show off a bit. Also, keep in mind Gianni is just 21 and starting his career -- reporting such strong efficiency results across several image formats (AVIF, WebP, Aperture) is impressive and worthy of celebration by the community!
- Tiles in AV1 go through the deblocking filter, so there won't be any seams after decoding. In fact, AVIF encoding solutions (like libavif) enable tiling by default. If there were seams, people would've noticed those artifacts and yelled at the libavif maintainers.
- *Because* JXL doesn't have a deblocking filter, you could argue that JXL effectively decodes to numerous "mini-tiles" -- each one equaling the size of a coded block. And indeed, you WILL see those boundary artifacts when quality isn't high enough for EPF, Gaborish and/or LF smoothing to mitigate satisfactorily. This is what Gianni's post covers.
- AVIF scales very well under multithreaded decoding scenarios, thanks to the excellent work of the dav1d devs. The main conclusion wouldn't have changed -- AVIF is significantly faster to decode than JXL.
- In progressive decoding, a very valuable feature is "bytes to first usable image". That's what the comparison is focusing on -- it's not a cherry-picked point at all. By usable: you can tell the pass isn't a "blurhash", but you can actually discern each element in the picture with reasonable detail. You can play with the JXL demo yourself -- JXL roughly needs 3x as many bytes to get to where AVIF is in quality, and JXL is still a bit more blurry in general. This applies to every image in the demo, not just the poke bowl.
- The folks who coded the JXL demo happened to use two passes for progressive AVIF, but you can use up to four -- including adding an even lower-quality "blurhash" pass, and/or a medium quality pass. Yes, it's desirable to control the number of passes and quality at the encode stage.
"For non-photographic images, the argument that “they should be vector images” doesn't hold up because many images could be vector images but aren't, and they can't be vectorized perfectly. “The world should be different” is not a justifiable defense against optimizing for the way the world actually is."
This is a good paragraph. I see people forget to apply that last sentence all the time.
Agreed. JPG is the most popular format for photography. PNG, the lossless format is great for diagrams and stuff with sharp edges. It can be "compressed" via dithering and quantization.
GIF is there... because it will always be there because it's just a hit that will never go away. It's also lossless (when discounting colour depth).
The new formats are interesting webp, avif, JXL and so on.
Jpeg classic is the clear winner IMHO and will probably never be less relevant than the new fancier formats. JPG even does text and sharp edges, reds, and so on well if you tell your process to take into account chroma subsampling!
Gif is a weird one because it's silently been replaced while keeping the name around. Virtually every software using the term "gif" actually uses a h264/vp9 video with no sound.
Modern video formats are so much better that they are a no brainer to use while the word gif just got used to refer to looping video without sound rater than the literal gif image format.
> PNG, the lossless format is great for diagrams and stuff with sharp edges.
But also, like GIF, it's pointless when lossless WebP exists and is supported everywhere. It's more efficient. Lossy WebP does not make as much sense though since jpegli entered the game.
OP has made https://halide.cx/iris/ which could make lossy WebP make sense, but it's not open source or generally available.
> The new formats are interesting webp, avif, JXL and so on.
WebP was introduced 15 years ago. New relative to JPEG perhaps, but certainly not new.
Gif is still there because it's still often the only option for frictionless video embedding. Embedded videos usually come with a video player that hardly ever quite works out well, often not starting automatically, not looping, or showing video player UI elementa that shouldnt be shown.
Also it would be nice to have a good standard vector format that isn't the complete kitchen-sink that is SVG, but we don't have that. We needed "jpeg but for vector graphics" and instead we got "html but for vector graphics".
So anybody saying "we should use more vectors" has to remember what the state of open vector graphics standards is.
In the context of the world it's all hair splitting, you can have a big photographic picture in png, or 1% compressed jpeg, or 1% jpeg converted to png. No new format can change it.
It seems to me that AV1 (the codec used in AVIF) has seen a lot more development in recent years, by virtue of being widely adopted for video. JPEG XL has not seen comparably massive adoption, perhaps owing in large part to Chrome rejecting it on dubious grounds (in spite of eagerly forcing the adoption of both WebP and AVIF earlier on). The pace of the reference implementation’s development has grown very slow, and most of the modest attention it’s been getting seems to have recently moved to the new Rust decoder, once the browsers finally made up their mind that’s what they wanted from the devs.
That considered, I don’t think it’s a fair comparison between the codecs. JPEG XL used to be far more impressive than AVIF; it’s great people (author included) have managed to push AVIF forward, but until similar efforts have been made for JPEG XL in earnest, I don’t feel like a comparison between their encoders says much about the codecs themselves. The author does take a guess on how much the JXL encoder could be improved, but that’s just that: a guess. It won’t be know until it’s been tried. And especially given the whole unfortunate history, I think JPEG XL really, really deserves a try.
It is getting its try, actively, in libjxl. People like to pretend AV1 got infinite resources; the reality is myself and one other contributor produced the vast majority of the image gains. I built Iris-WebP and aperture-alpha myself, from scratch. As a compression engineer, I think JXL is way, way harder to work with, and it would've taken me a lot longer. libjxl has community contributors, it is just an uphill battle with a codec like that. Same as WebP is an uphill battle due to its format restrictions.
That’s the thing, though: libjxl development hasn’t seemed all that active in recent years. The community contributors you mention seem quite far from driving the development, and some of them say that the usual devs have been busy with other projects (including jxl-rs as of recently).
> People like to pretend AV1 got infinite resources
I would not suggest that, but in another comment here you yourself say that SVT-AV1 (which you compare to JXL favourably in your article) has seen active involvement from ‘Meta, Netflix, Intel, independent contractors, and others’ – not to the community fork SVT-AV1-PSY and its successors contributing their improvements back upstream.
I can believe that JXL may very well be more difficult to work with, but am I wrong to assume you’ve been able to continuously focus on your own encoder (and apply your experiences from your earlier work on SVT-AV1)?
We can reevaluate when and if improvements are made. The problem with statements like this, is its really easy to miss the showstoppers when imagining what something could be. All plans are amazing until you have to actually do them in the real world.
As the saying goes: Never fall in love with potential.
The stated reason for Chrome was not ‘we need a memory-safe implementation’. It was ‘there is not enough interest’ and ‘there is not enough improvement over AVIF’. At the time, there was interest and there was improvement over AVIF (which Google has decided to support regardless of memory safety, interest, or seemingly any deeper consideration).
Memory safety as a condition for adoption was brought up only years later, and by Mozilla rather than Google. The JPEG XL devs, who’d offered to work on it if there was interest, got to work as soon as interest was proclaimed. You might say it’s a good thing for Chrome to have held off adoption until then, but that’s completely incidental, not because they cared. Near-zero efforts to be fair and responsible were made.
That JPEG XL prime computation is a pretty ugly DoS. Just selecting it in Finder, with the preview pane open, maxed out every core on my Mac inside a QuickLookSatellite that also ate 4GB of RAM while doing so - for a good 15 seconds. Not bad for a 2KB picture. It seems like Apple did not set sane limits on their JXL previewer.
It is, however, an incredibly cool demo of what the format is capable of. I'm not completely sure if an image format should be that flexible, but I'm impressed nonetheless.
When a format has so much flexibility, the world will glom onto the first thing that it solves and put it into the wild to solve that problem. The rest of the capabilities fall by the way side, yet not removed from the format. They're just ignored. MP4 can do so much more than the typical deliverable of a video stream and an audio stream. The spec allows for multiple video streams, multiple audio streams, subtitles, Flash like interactivity to allow self contained DVD style programming of menus to allow for chapter navigation, audio/sub selection, multiangle, etc.
MPEG4 supports interactive 3D scenes (read: games!) via bit-encoded VRML which can include JavaScript. I don't know any software which support this features (even without interactivity), but it is here.
I'd wrote reader for this bit encoding many years ago when company I'd been employed at made custom VRML engine for Samsung featurephones (project was dead on arrival as at this moment smartphones / Android become available and all this lineage of featurephones was killed).
None of that has fallen by the wayside though? I have seen examples of all of those in the wild except for interactive menus and multiangle. Multiple video streams is incredibly rare to encounter but I have run into it a few times.
The argument in favor of flexibility (and jxl) is that if you optimize things for the "average" web user (as the essay seems to be suggesting) then fairly mundane usecases require you to start juggling formats, support becomes spotty, and things start breaking. It's nice to have generous limits within which you can be confident that things will "just work" for the end user. Even just on my own system I'd much rather use a single format rather than dealing with app x not supporting format y.
tl;dr jxl is the mp4 of image formats and that's exactly why I like it.
The only things I agree with the essay about are progressive decoding and decoding speed. Particularly the latter badly needs to be improved.
Probably not; for PNG, the image size is declared in the header, so a decoder can decide immediately if it wants to decode the image or not. The output is bounded by the size of the image times the bit depth, and decompression runs in time proportional to output size. zlib bombs exist, but they don't affect png because a decoder can simply refuse to decompress past the size of the pixel buffer.
The primary problem with that image is that is has over 60 channels, which means it'll take 20x more time to decode no matter what. Incidentally, the JXL spec suggests that web browsers shouldnt't decode images with so many layers. Jxl-rs will probably start enforcing such limits by default.
> I believe Web codecs should be purpose-built, efficient, and narrowly scoped to the needs of the Web.
The post downplays the usefulness of versatility. I disagree. I'd prefer not to play the "which image format is best for this image and this use case" game and having to transcode between them. For instance, it would be great if I could have an HTML gallery showing pictures of my files as I store them on harddisk. Today these are JPEG, because it's the lowest common denominator. WEBP, AVIF are not supported photography tools (e.g. https://support.captureone.com/hc/en-us/articles/36000262921...) and I don't expect support to ever be added since it is not formats intended for photography.
I got an impression JPEG XL is not a single format, but many formats put under one brand (same as webp), you still need to choose these formats and transcode between them.
I personally find AVIF more versatile. I just throw images at it, and it does a great job. As the article identifies, JPEG XL performs worse than AVIF in general, but it's particularly bad at things like illustrations and screenshots. With AVIF I don't need to worry about that.
I've always found it annoying how most cameras only let you save their photos as some combination of JPG/PNG/HEIC/RAW, often without any adjustable quality settings or option to save several copies in different formats.
It would be great if their behavior could be customized in a more modern web-friendly way, like "Save the original photo as a 95% quality AVIF in this folder, and also as an 70% quality resized WebP in this other folder".
The camera's I've owned (Canon and, in more recent years, Olympus/OM System) all could do RAW, JPG, or RAW+JPG, or in some cases cRAW+JPG, with several quality settings available for the JPG side.
But remember, on a camera you're wanting to maximize battery life, image quality and certain key performance metrics. The OM-1 Mk II can burst up to 120fps of 20 megapixel images with locked focus or 50fps with continuous AF. Thats a huge amount of data to capture, process and write to media. I think we want cameras to optimize for that. It's trivial to dump the resulting files on your computer and then convert between formats to your hearts content.
Nobody has brought it up yet, but JPEG XL seems to be close in potential and flexibility to OpenEXR. It seems more a competitor to something like that--for use in image processing and digital art pipelines--than something like JPEG, WEBP, or PNG.
That said, I have converted my personal JPEGs to JPEG XL, because you can losslessly convert back and forth between the two for smaller filesize in JPEG XL with no quality loss, so I get free storage savings and can get the byte-for-byte original JPEG back if I need it.
I knew about the lossless JPEG to JPEG XL compression story before, but had no idea that it was a two-way road. That's truly f* impressive. Boggles my mind even more the fact this format hasn't been adopted widely yet.
JPEG is a lossy frequency-space compression stage followed by a lossless Huffman coding stage. The second stage is quite generic as such, essentially compressing a stream of bits.
So you can relatively easily replace the second stage with something better. And since it's lossless you can easily go back.
Dropbox[1] and others have exploited this for reducing storage requirements, converting back on-demand so the client doesn't notice.
1) AVIF has now been radically improved to the point where it's actually quite good in ways that previously it was not.
2) JXL will not be improved despite the fact that the performance of every other codec has always radically improved over time.
Everything else aside, including a few clear methodological errors, it's ahistorical and unsightly to be unwilling to imagine that future implementation effort will accomplish anything. Some might call it hypocritical.
It sounds like you don't recognize the relationship between text and subtext.
The entire post amounts to saying "JXL in its first iterations was better than AVIF's more advanced state of development and support, but AVIF very recently got better only after several years of widespread adoption, and I don't think JXL would too".
The arguments given against JXL cannot be reconciled with the history of codec development.
Note, that JPEG XL was added as a possible compression method for DNG files (Digital Negative - stores raw images with raw sensor data of a camera).
Because of it, for the past couple of years, all new iPhones and almost all Android phones (mostly Samsungs) already contain a JPEG XL encoder / decoder (to generate these DNGs).
I'm sure this is right about all the technical things, but the stuff about the requirements of a format for the web misses the mark IMO.
Normal people don't pick an image format based on whether it is suitable on the web or not. They want a format that works everywhere. If I download or upload a photo I don't want to have to do a lossy format conversion. If I'm writing an image processing tool it would be great if I can make it just support one input format that everyone uses, rather than "web" formats and "non-web" formats.
So I think a large part of the attraction of JXL is that it is a single format that works both for 10000x10000 lossless scientific images, and for 256x256 lossy web photos. You don't have to be an image format expert any more. Just always use JXL.
Definitely a shame about the technical flaws listed here though - especially decode time.
Professional web developers want to create a great experience for their users, so they go beyond simply serving whatever comes off a digital camera.
As the article identifies, JPEG XL is kinda bad at certain types of images, whereas AVIF does well across the board, so if you feel compelled to pick a single format to use, AVIF would be a better choice, but it's definitely worth optimising your web images for the web.
Also, JPEG XL is two codecs bundled into one, VarDCT and Modular. So, even if you're picking JPEG XL as "the one codec", you're actually picking two, and you need to choose between them at encode time.
That's an internal detail that doesn't really matter to anyone outside library implementors, or when you're choosing encode settings though.
It's the same in Opus. Technically it's two formats, but as long as they're one entity that's either supported or not supported, everything is good.
AVIF does seem to have at least a couple of downsides compared to JXL like max 12-bit depth, no JPEG reencode and worse recompression stability. I think they probably could have added those though, and then we wouldn't have yet another format to support for eternity. Oh well, they had their chance.
Much like WEBP, JPEG-XL is two different codecs in one. There's VARDCT mode, and Modular Mode. Modular Mode is normally used for lossless, but it can also be used for lossy as well. When you use Lossy Modular Mode, you get different kinds of compression artifacts than what you'd see in a JPEG file.
For Lossless: JPEG-XL wins, then WEBP, then PNG. (Sometimes lossless WEBP wins)
For Lossy: AVIF wins, then JPEG-XL, then WEBP, then JPEG.
Sorry for the dumb question, but I don't understand something in these graphs. Since it's x=speed and y=bd-r, is this test done at a fixed target quality/size?
I feel like JPEG XL could be a good RAW format for mirrorless cameras... something with huge flexibility but with the perk of being easier to view casually on other devices. And then that in turn could make it a more useful web format? Camera vendors are of course notoriously proprietary/stubborn.
Lossless JPEG XL is in the DNG spec since three years (v1.7). So, you can convert your proprietary camera raw files to smaller ISO standard compliant JPEG XL compressed DNG raw files (mosaiced, not linearized).
PureRAW can now output linear DNG's compressed with JXL. It's amazing the first time you use it seeing 25mb RAW files go in, get made linear, and pop out 8mb or 9mb, then toss them in your RAW developer of choice and still find all the dynamic range and such you'd expect from the original RAW. I'd been doing that on my own with a script that called Adobe's DNG Converter, which has the same capability, to convert older versions of PureRAW's linear DNG to JXL-based DNG files, but that's no longer necessary.
Unfortunately, at least as of perhaps a year ago, I couldn't find any other actively maintained software tooling that could reliably do what Adobe's DNG Converter was doing, and there's so much nuance to the world of RAW files that's not at all just a trivial one-shot prompt to Claude/Codex to roll your own.
Not linearized as in samples do not represent linear color space? I think that's untrue, as all sensor work I've done (a decent amount across many projects) are linear: double light = double photon count = 1 bit of sensor space. There are technically often some bends from physical and engineering effects (photon interaction with substrate has some variability, temperature affects things a bit).
Or is there some other meaning of "not linear" you mean?
You are thinking of DNG which is more of a container format. It can use multiple image formats internally to record the actual image, one of them being JPEG-XL.
iPhone raw images are actually a jpeg xl inside the DNG.
True. I would love to have lossless images (and video) out of my devices still. Not as a replacement for RAW but as a middle ground between RAW and lossy JPEG.
Not for quality reasons primaily but because keeping the first stages of the processing pipeline and the archival branch lossless solves some headaches.
There is no any «web» anymore. E-mail clients are web, news readers are web, image galleries are web, heck, even image editing software could be web (google:photopea).
And as such there should not be «web-optimized» formats anymore.
"Web optimised" really means "internet transfer optimised". Eg, the benefits would also be there for native apps that are downloading images from the internet, and they're not the web.
In practice "web optimized" is a soft copyright control where the image is read-only to the extent the only readily available software that can open it is a web browser.
In the post, I say "I think WebP was a bit too narrowly scoped"
This is not a coincidence, but I don't think it was that devs looked at WebP and thought "huh, the lack of 4:4:4 and 10-bit support makes this less compelling for our product despite being all over the internet" – I think it was just a matter of not keeping up. Except for Apple, not sure why they took so long to implement it.
Wasn’t WebP pushed pretty hard by Google for several years, until the (ever shrinking) rest of the ecosystem sort of caved in? My impression was that there wasn’t much interest until it became more or less inevitable because of that.
Can whatever the next new image format for the web will be please have a JSON block at the start giving
- dimensions
- filetype
- minimum required decoder version
- lossless: true/false
- a list of alternative URLs and mimetypes to older image formats
And it doesn't have to be JSON, as long as it's in a fixed location (looking at you, AVIF and JPEG), extensible and can be decoded by just reading the first 8KB or 16KB.
Then any future image format is a simple drop-in without requiring complex processing on the server side or a lot of complexity in HTML (not to mention CSS)
How ergonomic are the modern AVIF encoders? I like libjxl (and cjpegli) because they are really good at generating reasonably compact, high-quality images.
For every other image encoder I used I couldn't find one setting that would make compact, high-quality images across the gamut of inputs (e.g. things like comics that have extremely visible high-frequency content would look terrible at quality settings that looked good for many photographs).
Lossless was discounted due to webp, but doesn't webp lossless only use 8bit depth RGB? (I think it is important to have a separate file extension for lossless stuff anyway, otherwise it gets confusing quickly)
I have a lot of basic questions about the CVVDP graph. Is the X axis encoding or decoding speed? Is higher better on the Y axis? What format is Aperture? I assume "aom" is AV1 but it wouldn't hurt to document it.
x-axis is encoding speed, Y-axis is BD-rate where higher is better. aperture-alpha is an upcoming encoder from Halide Compression, no more details than that. libaom and SVT-AV1 are both for AVIF; libaom is the AV1 reference encoder.
What do you think about the fact that most perceptual quality improvements in SVT-AV1 have been almost only driven by external, non-paid enthusiasts such as yourself while the maintainers have been basically only targeting VoD and RTC?
Compared to JXL (which admittedly has almost nobody working on except veluca these days...) which was focused on it since the beginning, I think it really matters.
I would argue that even if JPEG XL isn't the best choice for Web images, if browsers don't support it then that will widely hinder its adoption for its non-Web use cases. Would you agree?
The scenario I'm thinking of is sending a photograph by email. Let's say Sally has just had her second baby, and wants to send baby pictures to her mother, the baby's grandmother. Neither Sally nor her mother are computer professionals, and they don't want to care about image formats. Sally wants to upload a file from her camera, attach it to an email, and send it. Her mother wants to click on the email and see pictures of her new grandchild. Neither one of them wants to have to convert the image themselves.
Let's say it's a few years in the future and Sally's camera produces JPEG XL files by default. (Which I don't think would happen if browsers didn't support it, for exactly the reason I'm about to articulate). If Sally's mother's browser doesn't support displaying JPEG XL, then although Sally (who uses a different browser than her mother) sees the picture in the email when she sends it, her mother writes back an email saying "the picture didn't show up, can you resend it?" And they spend a few back-and-forth emails before finally getting tech support from a friend who helps Sally convert the picture to old-school JPEG so her mother can see it.
If that's the experience for end-users, cameras would hesitate to switch to JPEG XL as a default format. Because nobody wants a hostile review from a user saying "My mother couldn't load my baby pictures, what kind of lousy camera are you making?"
So even if it's not the best format for the Web, I'm still persuaded that having universal browser support for a format intended for photos is an important factor, and devices like cameras will not switch to it as a default format until manufacturers are certain that browser support (and OS support, and electronic photo frame support, and so on) is nearly universal.
None of that takes away from the argument "Other image formats are better for saving space on the Web", which is the main thrust of your post. But I do disagree with the last line, "I'm just not personally convinced we need it in browsers any time soon." I believe that if browser adoption is lacking, adoption of the format in places where it makes lots of sense (like cameras) will also be slow.
> I would argue that even if JPEG XL isn't the best choice for Web images, if browsers don't support it then that will widely hinder its adoption for its non-Web use cases.
Both Firefox and Chrome [1] have committed to shipping JPEG XL later this year. Safari has supported JPEG XL since 2023, though their implementation doesn't support progressive images yet.
So the major web browsers will support JPEG XL later this fall.
> But I do disagree with the last line, "I'm just not personally convinced we need it in browsers any time soon." I believe that if browser adoption is lacking, adoption of the format in places where it makes lots of sense (like cameras) will also be slow.
I'm not even personally convinced it is useful for cameras. Sally's situation isn't particularly bandwidth or feature-constrained, so JPEG or PNG work. Maybe JXL is solving problems that don't exist?
I think it is a potentially good camera format, good medical & scientific imaging format, good RAW compression format (Apple uses it in some newer iPhones for this), good media interchange formats for tools like Photoshop (think about storing all of your layers inside of one JPEG XL that's fully compatible with .psd files), and more. It is incredibly expressive and versatile, which is what makes it so risky on the Web.
Thank you for an interesting article. You’ve helped AV1 come a long way!
In the ‘Lossy Compression Efficiency’ section, you compare the codecs using various metrics, but I don’t think you say anywhere what quality the images were encoded for. Did you forget to mention that or am I just reading things wrong?
(I assume BD-rate tells us how similar the images look, but I also assume the values would change if the encoders were made to target different qualities, hence why the intended quality seems quite important to know.)
It would be nice to see the actual R-D curves for the codecs instead of compressing them into a single number. Also, what is BD-rate computed with respect to, jpegli at p0?
those issues aren't real. they're nuicense suits by a patent troll. a couple companies will settle cause it's easier and cheaper, but if they ever try to go after someone big they'll fight it and get the patents invalidated for covering 30 year old work
I like how every time we have a codec fight no one seems to care very much about how long it takes to encode these files. Like I get it, the amortization schedule often works out, but there are scenarios where images need to be generated dynamically and will only ever be downloaded once.
It's very hard to beat the encoding performance of libjpegturbo, even with an asic.
> It's very hard to beat the encoding performance of libjpegturbo, even with an asic.
Pretty much any platform with a hardware jpeg encoder beats libjpegturbo. So probably all smart phones, large scale CPUs, even tiny few $ microcontrollers like ESP32's have hardware encode/decode that outperforms libjpegturbo.
I kind of settled on avif. I am not at all implying avif is perfect, in particular at high compression I notice the quality isn't quite as good as often advertised. For similar size compared to jpeg, avif is divine; and I also found avid better than webp in my own tests, so I switched to it. I don't quite see JPEG XL being really significantly better though. I think a really big problem here, even aside from Google trying to force deadlock people into its evil monopoly structure, is that we have competing formats (avif, jpeg-xl, webp) and that's IMO not so great when we want to have "one format to rule them all" that's better than jpg or png or gif. JPEG-XL is kind of a late starter here; if it is not really significantly better than avif or webp then I do not see it will gain any real foothold in the coming years.
If JPEG XL doesn’t become useful on the web, is it really likely to become popular with camera manufacturers, professional image editing tools, etc?
What does it offer there that existing workflows can’t support? Do those advantages make up for the transcoding that every web publisher would need to do to make the outputs useful on the web?
> If JPEG XL doesn’t become useful on the web, is it really likely to become popular with camera manufacturers, professional image editing tools, etc?
I suspect that eventually, the browser makers that are reluctant to add JpegXL support will do so, even if reluctantly, and so it will eventually "become useful on the web".
The reason why is Adobe added JpegXL as a compression format for PDF's, and as every browser maker wants their browser to also be a "PDF viewer", this means they must include a JpegXL decoder to be able to support PDF's going forward. If they must have a JpegXL decoder anyway, it is not that difficult to also add it as another supported format for the <img> tag.
Most people using dedicated cameras shoot in RAW, then use a program to process and export the photos afterwards. So camera manufacturer buy-in isn't super important.
I've been exporting in JXL from Lightroom for a little while now, you get slightly smaller image sizes and HDR with no real downsides. On the web I imagine this will translate to higher quality images on social media since platforms can get more out of the same file size. It will also likely be the end of HEIF which is a pain to deal with due to patents.
The second paragraph doesn’t follow from my question, because it assumes JPEG XL does become useful on the web. The author believes AVIF is too far ahead already.
Web publishers should definitely be stripping metadata at least, and transcoding isn't much harder. For anyone who cares about bandwidth, transcoding to efficient formats is non-negotiable; if you don't, then why do anything? Just ship PNG, who cares?
I think one of the compelling use cases for camera manufacturers would be an interoperable format for editors. Since JXL has support for so many channels, you could load your image into an editor, edit it, add layers, etc., and export as JXL, which could be used for other things.
> Web publishers should definitely be stripping metadata at least
No, they shouldn't. Not blindly. Metadata can include copyright license information, such that stripping it violates the license to reproduce the image.
> Progressive rendering (which AVIF supports) decodes a low-fidelity rendition before the full image arrives. AVIF didn't support progressive rendering for a while, and during that time I believe it was deeply oversold. Now that libavif has implemented it (it was always possible), the conversation appears to be over.
This is false. AVIF does not support progressive decoding/rendering. What the author is referring to here is image layering. A lower resolution image layered below the full resolution image, which is loaded and rendered first. That is not progressive decoding/rendering. It is a thumbnail.
Unlike AVIF's false advertising, JXL truly supports progressive decoding/rendering. With JXL, you do not first load a thumbnail before loading the actual image. The lower-quality image that JXL shows while decoding is derived from the data of the actual, full-resolution image.
> A lower resolution image layered below the full resolution image, which is loaded and rendered first.
I'm curious, where did you learn progressive AVIF works like this? Have you actually read the spec, or does your understanding comes from somewhere/someone else and never challenged the truthfulness of it? Progressive AVIF is truly "progressive" -- it never involves "loading a thumbnail" or "layering an image over another".
In reality, each pass (up to 4) can refine previous ones (thanks to AV1's inter-encoding toolset), avoiding storing redundant information between passes. The viewing environment doesn't need to render a given pass if a subsequent one has already been downloaded. Finally, scaling is configurable -- you can have your first pass already be at full res, just at a lower quality.
Hope this helps clarify how progressive AVIF actually works under the hood.
> A lower resolution image layered below the full resolution image, which is loaded and rendered first.
Unlike a thumbnail, higher-resolution layers can be predicted from the lower-resolution layer, so those bits are not wasted. That is not possible by layering <img> elements.
You're wrong. AVIF does support spatial layering where the full-resolution image is derived from the lower-resolution layer, and cannot be decoded independently.
Yes, the format is not inherently progressive. But having the fine steps in progressive quality that JPEG-2000 and JPEG-XL have has less general usefulness than the amount of words complaining about it.
Not sure if the difference is materially relevant to UX at all. JPEG XL achieves progressive rendering at a great cost to its selection of coding tools, so I side with AVIF's approach.
Yes, if you look at the demo, the "progressive" AVIF loads a visible image at 8.5KB, and at that point, it looks better than the progressive JXL. However, that is ALL the AVIF shows until the image has fully loaded. At around 98KB, the JXL looks significantly better, and at around 240KB already looks really close to the final image, while the AVIF still looks terrible. At 280KB when the AVIF finally loads, they look identical.
Progressive rendering is just a different way to layout the pixel data. Embedding a thumbnail is storing two distinct images. In other words, progressive rendering should be more efficient space and bandwidth-wise.
Of course it does, with one you have to render twice and store two layers which costs you both compute and storage. With the other you can just take the image mid decode at a point and display it. Single decode operation, no layer mess.
The difference matters, as it means that AVIF's "progressive decoding" serves no technical benefit and is only a minor ergonomic benefit: On a website, you could achieve the same effect simply by layering two <img> elements on top of each other, one with the thumbnail and one with the final image.
If layering to <img> elements is fine for your use case, then it simply means you have no need for progressive decoding.
How does progressive rendering actually that most OS GUIS are not multithreaded ?
The preview in finder is still going to block. Im saying this as a MAC user speaking of experience browsing mounted drives that sometimes are slow and it feels like the window freezes up.
Thumbnailing happens in a background process and shouldn’t block the main thread; rather hangs are usually because fetching xattr over SMB is slow and Finder will block until it’s enumerated the metadata of every file in a folder.
Preview actually does use progressive rendering for large enough images, even from SSDs. You can tell because opening an image will be blurry for several seconds, even when the full size image could have been decoded in a quarter second or less.
We all know these aren't purely technical reasons, it's to break the monopoly of one Internet Company's decoder format portfolio. You can't let one Fruit Company's format be the thing either, so it's basically a L for engineering but a W for pleasing everyone TBF.
AVIF is royalty-free, with open-source implementations not developed by Google. Google's implementation is libaom; as you can see, SVT-AV1 beats it. SVT-AV1 is developed by a number of companies – historically Meta, Netflix, Intel, independent contractors, and others. I worked on SVT-AV1 myself. I don't see how this is a bad thing for everyone, even if Google drove standardization of AV1?
There were something like 40 companies involved in AV1 standardization. Quite a few technical contributions did not come from Google, and quite a few of Google's proposals were substantially modified by feedback from others before they were included (and not all of them were eventually included).
Source: I lead Mozilla's technical contributions to AV1.
Had a lot of the content in this article came out 4 years ago I would have agreed. At least we finally don't have a fake Image Coding Comparisons [1] that tries to undermine JXL.
Ignoring AOM and AV1, I was the first few on HN apart from its author supporting JXL from the start, I would argue the biggest case against JPEG XL is JPEG li.
Jpegli offer enough quality improvement and advantage without introducing an entirely new codec. And all of a sudden the bar for next image codec now needs to be even higher.
The chart showing jxl-rs taking 1209ms to decode a 5456x3632 image in a single thread is a little damning, but is there an equivalent benchmark showing multithreaded decode performance? Clients tend to have an abundance of threads these days.
The JPEG XL report [1] measured between 240-270 Megapixels/s on 6 cores using the C++ implementation (disclosure: I was responsible for its SIMD/threading), about twice as fast as the then-current libaom.
Measuring on a single core is deeply misleading because our code was designed to scale well. I believe AVIF requires tiling in order to parallelize, which causes artifacts at tile boundaries.
It’s a measurement error: the `hyperfine` command uses `jxl_cli --speedtest` which, by default, does a warmup run that ends up in hyperfine’s measured time.
The time would be less, but you still need to power those cores. Single thread performance can be a good indicator of what it'll do the battery on your phone.
CPU power is proportional to frequency^2. Running on 4-6 little/efficiency cores (which are widespread on mobile) is likely faster than one big core, and uses less energy.
jxl-rs is a relatively new implementation, not yet optimised for speed. It’s hard to say how much faster it’ll get, but I assume it would at least get near libjxl’s level.
These sorts of things always talk about progressive rendering. Who actually likes progressive decoding? Like...what year is it?
I don't want an image to appear in any form until its loaded. I never need to see a blurry placeholder, and there is zero value in that even with bad connections, but the situation is farcical when everyone has ultra-fast connections everywhere.
This is similar to pages that use custom fonts but will happily show the text as quickly as it can, and then suddenly restyle/relayout the page when the custom font loads (Flash of Unstyled Text - FOUT). It looks terrible and is jarring. Progressive rendered images are the same.
I disagree with this. If I'm in a poor connectivity situation, a preview can help me quickly decide if an image is worth waiting for.
I'm not talking about blurhash here - those are 'cute' at best. I'm talking about previews that let me determine the subject of an image.
I was on a train recently and an image preview X delivered to me was enough for me to tell that the image was a particular meme format, and thanks to context, I knew enough about the image, and didn't bother waiting for it to load.
You've left some 36 comments on this submission (which is honestly weird as HN usually rate limits to avoid that sort of aggressive participation), and your comments seem extremely...cherry picked. In another comment you dismissed the bandwidth savings of JXL because connections are so fast that eh, who cares, and in this case you herald the importance of progressive rendering because connections are so slow.
Are you the author of the submission? Literally never seen someone so motivated in a conversation before.
I wasn't really sold on the argument initially, given they admit there's some real lossless usecases, but this is a good bit from the conclusion:
> Not to mention an additional compatibility headache now exists for anyone just trying to download an image from the Internet and use it somewhere – it was hard enough to get widespread WebP adoption, and I don't think it's worth doubling the pain by having to climb the same hill for AVIF and JPEG XL. Especially when JPEG XL doesn't appear to add anything to the Web platform.
It is very annoying downloading an image for the web and then trying to upload it somewhere else also on the web during these transition periods.
There exist lossless use cases, for sure. I think most people would be well-served by high-fidelity lossy that saves a lot of bits while still looking perceptually identical. Whoever isn't served by that most likely doesn't care about size savings, and can stick with lossless PNG.
The problem with that is that the idea many stakeholders (especially big platforms) have of "perceptually lossless" is actually compressed to hell garbage. The only way you as a user can ever guarantee actually perceptually lossless is to use a fully lossless format.
Worth noting that this progressive AVIF, when viewed in Chrome, has only two states: a "base layer" which pops in around 8KB, and the full image which appears 270KB later. The comparison JXL continues to refine during most of the download, so it winds up looking substantially better than the AVIF at around 95KB loaded, and looks pretty good (almost as good as the full 280KB AVIF) by 175KB. I suspect that there are a lot of knobs to turn for both progressive modes, but this particular case could definitely be cherry-picked to favour either codec.
Progressive AVIF is very flexible: it supports up to four passes, at configurable quality and dimension scaling levels. You can have any given pass reference up to two previous ones for refinement (thanks to AV1's strong inter-encoding capabilities), and you add filters to non-final passes (like blurring) to achieve a desired loading aesthetic.
That JXL page happens to use two passes, but the knobs are there to customize the experience to fit the use case.
Because of Gianni's great post, I've decided to go full throttle on rewriting and finally publishing the JXL vs AVIF post after deciding to partially shelve it last year.
This should be especially interesting looking at the differences between my testing and Gianni's.
Is there a way to have fast on-the-fly WebP encoding? When i checked it, it was unusably slow (multiple seconds for large images), but maybe that was the implementation. That alone made JXL far more interesting to us.
The form of JPEG-XL that can lossless convert to/from traditional JPEG is exciting tech that should be adopted universally. The non-backwards-compatible version of it seems redundant with AVIF.
Author entirely misses the case for what many people want it - re-compressing old JPEGs that they have no better sources for into JPEG XL with out decode-encode loss
> JPEG recompression is the ability to losslessly re-encode JPEGs as JXL images while saving bits; the oft-cited number is 20% savings. However, the user pays for this in decode time, as recompressed JPEGs take ~33% longer to decode
"but strong mode-decision pipelines can pick the right mode for the job and save lots of bits" - citation needed. just a bit above author claims lossless is not useful for web, disregards modular jxl that uses nearby pixel predictors (even though it can be lossy, too), then produces this claim against vardct. spoiler - dct frequencies ARE using "nearby pixel values"
Depends on your location. While I have a decent internet connection at home, the mobile one is trash. Good for IM and not much else.
Most of the people I know only have the mobile connection, pay a lot for the privilege, and while speeds are generally good (LTE and up), the monthly cap for almost all of them is 10-20 GB.
Formats that aim to be web standards should try not to be patent encumbered. There was a lesson to be learned from the Unisys debacle in the 1990s. If you don't want to reencode for the web, use a device that captures in a format that can be shared on the web.
You should never transcode lossy source files because there is generation loss in quality.
There is still a lot of reason for Apple to switch from HEIC to JXL for photos going forward since HEIC is patent encumbered so it will never see widespread use.
Well, JpegXL does have one really cool feature: you can transcode jpeg to jpegxl (and back) losslessly. For jpeg to jpegxl it'll save something like 15-20% in size.
Rather than AVIF or JPEG XL or WebP or HEIF or any of that stuff, my actual ideal choice that I wish everyone used is just good ol' JFIF. I like that I can take a file downloaded from the modern Web and open it on my '90s and 2000s computers. I emphatically do not care that it's some marginal percentage “““more efficient””” — more efficient for Google and Apple and Amazon and all the other silo providers who are moving more data every day than I will produce in my entire life. But why should I have to suffer backwards-incompatibility for their sake?
Backwards compatibility is cool; stop the fucking churn! I have done this just within this past week, in fact, when I moved a JPG over to my Mac OS 7.6.1 machine (PowerBook 2400c!) to use as a new desktop wallpaper†.
Lossless dismissed? 11% isn't nothing, that's trillions of images out there. Mozilla's own data shows JXL lossless beating AVIF and WebP. That's the one weakness of avif that bothers me, for lossy and speed it is brilliant. Companies may have another itch with the misleading licensing:
AVIF's "royalty-free" is under active legal attack (Dolby v. Snapchat). JXL has clean ISO commitments so no such suit would be possible. If "free" matters, JXL is safer.
Perceptive quality with the latest AV1 caught up, but that's a rigged timeline. Chrome supported JXL "late", then pulled it altogether. AVIF did improve further yes, it had web usage, it was behind when the race was meant to start. Why would JXL continue to optimize for web once the major browser refuses to support it.
I agree that the choice for JPEG XL is mostly politically motivated: it isn't Google. And its name is derived from JPEG, which is an IETF standard which gives it more clout.
It is Google. The JPEG XL standard evolved from a codec Google made, Google was involved in the standardization process, and Google heavily contributed to the reference implementation of JPEG XL.
The article makes a good point: JPEG XL is amazing but not specifically for the typical Web use cases, compared to AVIF. But the conclusion doesn't follow. Having an excellent and versatile format supported by browsers is very useful!
Maybe a lossless re-encoding of my website JPEGs to gain 20% size is not worth the 33% longer decode, and maybe the website doesn't need very high resolution images or more than 12 bits per channel. But my personal archives can definitely use that and it's great that such files can be viewed everywhere without specialized tooling, including served on the intranet and indeed the Web.
In summary JPEG XL easily beats AVIF on the not-so-long tail of use cases and having compatible viewers everywhere is quite useful. And with JPEG XL becoming part of PDF, it will soon be common use cases too.
As for the rest of the article: there are interesting points in the benchmark section but I think it's too early in the JPEG XL adoption cycle to draw conclusions. One thing bothers me though: There is a single picture comparison (with tag line "results speak for themselves") and I find it quite misleading: it's just picking one point on the "bytes received" line that looks best for AVIF compared to JPEG XL. Try it yourself and you'll see JPEG XL shows something already at 2KB while AVIF has nothing until 8KB, and JPEG XL looks better than AVIF after 100KB.
+1, this is super unfair to show the one point in time where AVIF progressive looks better - right after it receives its 'preview' (which as you say is 4x as big as JPEG XL's).
I value integrity, especially when communicating results. This is shameful.
(Disclosure: I worked on JPEG XL)
I’ll just repeat another comment here:
“For progressive, I think it's better to show the user something that's obviously a preview, but still has enough detail to be able to know what the picture is of. If you're showing the user something that they may mistake for complete but poor quality, that's a bad experience.”
-jaffathecafe
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For progressive, I think it's better to show the user something that's obviously a preview, but still has enough detail to be able to know what the picture is of.
If you're showing the user something that they may mistake for complete but poor quality, that's a bad experience.
Depends on the user. Some users are more sensitive for flashing images. Some users have very slow or unreliable network connection. Some sites have bigger images. Some sites (such as ecommerce) have higher quality and resolution needs.
Some users have uncorrected astigmatism. In the general population, the average uncorrected astigmatism typically falls between 0.50 and 0.75 diopters (D), and ~15 % more than 1.0. The high astigmatism people will see images blurred in any case and don't benefit from the fine structural detail JPEG XL can give. People with glasses and the lucky ones with low astigmatism will see the details clearly.
Sometimes passionate ends of different quality of vision seem to have a discussion on what makes sense as the web quality, with one emphasizing quality 40 being more than enough and another requesting a quality of 95.
The same kind of individualism exist also in temporal cognition and perception.
The quality of the preview layer is somewhat under the control of the user though.
And that comparison was made for a JPEG-XL focused site, and uses quite large images that are then scaled down dramatically (at least on mobile) for display which is probably not an ideal visual test anyway (but possibly necessary for there to be enough time to see any difference)
That's a good point.
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Agreed. Browsers should support general-purpose image formats. I'm not interested in another “web codec” that's not good for anything but passive delivery.
> Maybe re-encoding my website JPEGs to gain 20% size is not worth the 33% longer decode
I changed all my .jpg files to .avif a few years ago. The benefit I get is much more than 20%. Now there is some loss when I use high compression with .avif, in particular via gimp - but other than that, I gained a lot of file size here, definitely much more than 20%. It also depends on the image at hand; I noticed that images with a ton of details, such as if you photograph a garden, takes more space. But for simpler images, I have easily gains of about 60% or 70% compared to jpeg, with no or almost no loss in quality. Whereas if I were to use jpeg compression, the quality loss would be insanely high. When I noticed this, I decided to abandon .jpg for my own use cases. I had to choose back then between avif and webp and while webp is fine, I found .avif was slightly better for the use cases I had.
I don't quite know how much jpeg xl performs, but you mentioned JPEG so I had to comment on that 20% statement as I found it way too low.
I also find the claim "longer decode" not correct. I have some photographs of gardens and the file size is huge, in JPG. When I compressed and changed these into .avif, the resulting page loads soooooooo much faster now when having used avif and a considerable but acceptable compression of it. It is just no comparison at all - avif beats jpg with its eyes closed.
Sorry if that was confusing, I have edited my post to clarify a bit: That sentence was about a feature specific to JPEG XL, which is that if you have JPEG files you can re-encode then as JPEG XL to save space without any loss of quality. It's nice for peace of mind, you can bulk convert a large archive and you know you still have the same pixels everywhere (later you can even turn them back to JPEG without loss if you want). AVIF cannot do that. Now if you are OK with some loss in the conversion, you can also do much better than 20% with JPEG XL.
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That 20% gain is for the lossless re-encoding. It's not possible with .avif AFAIK. If you allow minor loss, jxl can save much more space.
It sounds like you lossily re-encoded lossy JPEGs to AVIF, am I reading that right? If so, you're automatically suffering from generational loss there, it can't be the basis of any coherent argument.
The entire article is extremely cherry picked, and it's notably that there are a couple of people leaving dozens of comments in here each (which is odd as normally HN gates that sort of gross overrepresentation). Like >10% of comments in this 300+ comment discussion is one single person, endlessly changing positions based upon what makes JXL worst.
It's bizarre. I've never seen a format see such ridiculous attacks.
If you're going to make claims of bad faith about other users like that you should link and quote.
>Maybe a lossless re-encoding of my website JPEGs to gain 20% size is not worth the 33%
I was unpleasantly surprised when jxl's reference encoder dropped critical exif tags for no reason whatsoever from my personal archives. Turns out their lossless preset wasn't really lossless.
And then webp to JXL conversion also produced different viewing experience results as ffmpeg's webp decoder wasn't handling ICC correctly.
I'm now very cautious of any "lossless" re-encodes.
> Maybe a lossless re-encoding of my website JPEGs to gain 20% size is not worth the 33% longer decode,
And pray tell how much of the waiting for page is used on decoding image (vs transferring) and how much faster the image gets on the machine when it's 20% smaller on average connection?
My guess is that time saving from bandwidth decrease more than compensates for that
Well it obviously depends on the connection, but at 3g speeds and higher, the decoding time outweighs the fairly minor bandwidth saving.
And if you're displaying a cached image, the bandwidth use is zero, but the decoding still happens.
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It depends on your network speed, how big the image is, the compression rate of the image, and how fast your hardware is.
A potentially major issue I have with AVIF is that because it is based on a video format, any hardware decoding support AVIF will get is likely to be restrained to common video scenarios. This can result in eg. only 4:2:0 YUV being supported by hardware decoders, as that's the upper limit of AV1 Main Profile (and thus the limit of AVIF Baseline Profile). And 4:2:0 is just a poor fit for certain categories of images (like various kinds of illustrations, screenshots, etc). I would not be very happy about a web where lossy 4:4:4 image compression would be heavily discouraged with modern formats.
Also, good lossless compression absolutely does matter for the web as well. Lossy images just cannot be used in all circumstances - like when comparing compression quality (especially of videos), for example!
EDIT: To give an additional example, pixel art is an entire field of art (which is very much still active today) where both lossless compression is a must and where 4:2:0 would be absolutely catastrophic for quality.
> And 4:2:0 is just a poor fit for certain categories of images (like various kinds of illustrations, screenshots, etc).
I'd go even further and say that 4:2:0 is unsuitable for still images, period. Even for cases where it would be a suitable tradeoff for video. And even for video there's a significant chunk of content where it's undesirable.
In general I think we've come to accept some pretty gnarly limitations on image quality that really should not be such a given. 8 bits per channel is another one. You actually really do notice the banding with the naked eye in a fairly large range of situations, and if everything is 8 bits per channel then it gets really easy to exacerbate the problem on edit. Dithering in 8 bits per channel isn't really a solution because it's hard to do and it gets lost in compression quickly.
4:2:0 is the main reason why most games look like crud once they've passed through any mainstream video encoding pipeline. That being said, the bitrates used for streaming games and VoDs are so low everything looks like mush anyway and millions still watch that.
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Luckily, 4:4:4 AVIF is supported in Firefox, Chrome, and Safari, right now. This won't ever regress.
Browsers already fully support 4:4:4 AVIF and are not going to regress on this, as it would be a huge compat issue.
It isn't clear whether AVIF hardware decoding will ever be an advantage, but for video formats, Firefox and Chrome already pick between hardware and software decoders to ensure the content plays correctly. Safari is much flakier here, but again, for images, they're not going to regress on 4:4:4 AVIF support.
Lossless AVIF encoding is inferior to JXL though, the article oddly dismisses lossless as a valid case for the web so it ignores the core argument that lossless is critical for some type of content.
I find the hardware support argument far more compelling that diminishing the value of lossless publishing.
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There have been a number of experiments to use hardware decoders for images in browsers, all of which have fallen flat; not even Safari does it for AVIF or WebP. Thus, 4:4:4 AVIF is supported absolutely everywhere. Feel free to try it now. I can see how hwdec is compelling for JPEG XL in theory, given how slow decoding is.
In the modern age image decoders need to handle untrusted inputs, and the big players rarely use hardware image decoding, even when it's available, because it's so hard to rely on its memory safety.
Several 'zero click exploits' have involved image/document format decoder bugs, as messaging apps and file browsers will often generate preview images the moment an image arrives.
All Browsers do use hardware decoding for video though, I doubt safety is a major factor.
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Isn't the same true for video decoders, though?
Wait, DAIZ!? I genuinely did not expect to see you here chiming in. Still appreciate much of your 10 bit anime advocacy from way back.
I don’t think hardware decoders are used for images. They are light enough you can do it in software.
AVIF's support for non-photographic images is covered in the article. It supports lossless.
Yes, I know the format supports it. The question is, will hardware decoders built primarily around video use cases? And if those kind of hardware decoders end up forming the majority of hardware decoders for AVIF, will we end up in a future where using the full range of the format is heavily discouraged because it won't be supported by hardware decoders?
For comparison, it was possible to do 10-bit video with H.264, but 10-bit video didn't see any mainstream adoption with it because hardware decoders generally didn't support 10-bit H.264 video. Only when newer formats came around and specced 10-bit support as a baseline necessity did we start to see wider adoption for it. And well, the baseline specs (main profile) for AV1, which AVIF is based on, are limited to 4:2:0...
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It's not lossless if you have to convert to YUV first.
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I'm not super familiar with AV1/AVIF but I do have extensive experience using h264 for desktop streaming, and all major implementations support 444 in hardware and software, and I doubt more advanced codecs/image formats have a limitation like this. Asked ChatGPT and it also claimed there's no problem with 444 and AVIF/AV1.
> I'm not super familiar with AV1/AVIF but I do have extensive experience using h264 for desktop streaming, and all major implementations support 444 in hardware and software, and I doubt more advanced codecs/image formats have a limitation like this.
This is a good helpful comment containing relevant information from personal experience.
> Asked ChatGPT and it also claimed there's no problem with 444 and AVIF/AV1.
This part is useless, there's no one who cares what a LLM thinks that can't just prompt it themselves.
Then chatgpt missed an obvious issue, nvidia definitely have had shortcomings in the hardware implementation of coder/decoders only supporting 420 in nvenc/nvdec. One obvious problem with that was that it affected premiere.
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I'm pretty sure 444 h264 fails to decode on iOS Safari due to poor support in the hardware decoder.
Strange blog post. Given that it's from a developer of proprietary and paid commercial encoders, the inclusion of their upcoming "aperture-alpha" encoder on the charts that are purportedly about JPEG XL makes this feel like a marketing piece of some fashion. Certainly, they advertise their Iris-WebP encoder throughout the post, with an implication that if you haven't paid to the author for it, you're not using WebP correctly, I guess?
Moreover, there are some methodological oddities. For example, JPEG XL decoding is tested in single-threaded mode when it's optimized for multi-threaded decoding (where AVIF has artifacts from tiling). Also, the tested command is "jxl_cli --speedtest", which means that the benchmarked time includes the warm-up procedure of the "--speedtest" flag, rather than the pure decoding time.
Another example of this is progressive rendering, where the comparison moment is chosen at a local maximum that favors AVIF. JPEG XL materializes a full frame much sooner than AVIF, and starting at, say, the 96,256 B mark, it looks better than AVIF until the full image is loaded.
I expected one of these bad-faith readings, so I can address that Aperture is mentioned once and Iris-WebP is only shown in numbers, because I have access to these encoders and thus they cannot be ignored. The only encoders I heavily advertise here are the incredible open-source AV1 encoders, that I contributed to for free and I think people should use. Also, not sure where you infer that point about WebP; libwebp is a fine encoder.
AVIF does not have artifacts from tiling any more than JPEG XL has artifacts from being JPEG XL; if you read the details post at the bottom, you'd see there's a 0.5-1.0% BD-rate regression with tiles, which is effectively a rounding error.
For progressive, JXL shows a blurry mess for the majority of its decode, while AVIF shows a crisp image that clearly shows what is in the image. Go ahead and try the demo yourself! AVIF also supports more than one layer, but I used Team JXL's image on purpose to show that even there, AVIF looks better for 90% of the decode time. You need to watch what I'm showing you instead of adopting the most bad-faith reading because some things are mentioned.
> For progressive, JXL shows a blurry mess for the majority of its decode, while AVIF shows a crisp image that clearly shows what is in the image. Go ahead and try the demo yourself! AVIF also supports more than one layer, but I used Team JXL's image on purpose to show that even there, AVIF looks better for 90% of the decode time.
I'm not sure I agree? IMO after about 30% most images look better on JXL than on AVIF, the exceptions being the pigeon, which looks better on JXL after 43% (still less than half) and the sunflower, which looks better on 66% (but you can clearly see what's on the image a lot earlier). Also, blurry convey better the idea of loading and the AVIF version may have some weird artifacts / look weirder (although that's subjective), for example the Quechua woman's eyes are very distorted on the progressive AVIF and, on the Poke bowl, some of the seeds on top of one of the top radish pieces are kind of missing / look like a shadow (while other seeds of the same size appear). In contrast the JXL version is usually blurrier and less saturated at the beginning but is more "uniform/reliable" (distorts all of the "objects" more or less the same), and later it looks finished but actually isn't (which may be a problem on its own).
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Surprised and disappointed to hear "bad-faith reading".
I have seen AVIF tiling artifacts myself. Hand-waving them away by appealing to a metric that averages across all image pixels is not convincing.
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It also compares the total time for jxl-rs's benchmark mode (which does a warmup and a test decode) for 16-bit RGB against 8-bit WebP to 4:2:0 YUV.
Hi there! I'm Julio (co-developer of libaom and SVT-AV1's tune IQ). Here there are some points worth mentioning, because I'm catching a whiff of bad faith with your comment that honestly needs to be called out:
- The inclusion of his two proprietary encoders (Aperture and Iris) just serves to further support the argument that JXL encoder devs have work to do to perform at the frontier, while also proving you only need a person or two to do so. The two FOSS AV1 encoders in the compo (libaom and SVT-AV1) are enough to prove this. Given that blog posts often double up as a way to show-case projects, I think it's fair game to show off a bit. Also, keep in mind Gianni is just 21 and starting his career -- reporting such strong efficiency results across several image formats (AVIF, WebP, Aperture) is impressive and worthy of celebration by the community!
- Tiles in AV1 go through the deblocking filter, so there won't be any seams after decoding. In fact, AVIF encoding solutions (like libavif) enable tiling by default. If there were seams, people would've noticed those artifacts and yelled at the libavif maintainers.
- *Because* JXL doesn't have a deblocking filter, you could argue that JXL effectively decodes to numerous "mini-tiles" -- each one equaling the size of a coded block. And indeed, you WILL see those boundary artifacts when quality isn't high enough for EPF, Gaborish and/or LF smoothing to mitigate satisfactorily. This is what Gianni's post covers.
- AVIF scales very well under multithreaded decoding scenarios, thanks to the excellent work of the dav1d devs. The main conclusion wouldn't have changed -- AVIF is significantly faster to decode than JXL.
- In progressive decoding, a very valuable feature is "bytes to first usable image". That's what the comparison is focusing on -- it's not a cherry-picked point at all. By usable: you can tell the pass isn't a "blurhash", but you can actually discern each element in the picture with reasonable detail. You can play with the JXL demo yourself -- JXL roughly needs 3x as many bytes to get to where AVIF is in quality, and JXL is still a bit more blurry in general. This applies to every image in the demo, not just the poke bowl.
- The folks who coded the JXL demo happened to use two passes for progressive AVIF, but you can use up to four -- including adding an even lower-quality "blurhash" pass, and/or a medium quality pass. Yes, it's desirable to control the number of passes and quality at the encode stage.
"For non-photographic images, the argument that “they should be vector images” doesn't hold up because many images could be vector images but aren't, and they can't be vectorized perfectly. “The world should be different” is not a justifiable defense against optimizing for the way the world actually is."
This is a good paragraph. I see people forget to apply that last sentence all the time.
Agreed. JPG is the most popular format for photography. PNG, the lossless format is great for diagrams and stuff with sharp edges. It can be "compressed" via dithering and quantization.
GIF is there... because it will always be there because it's just a hit that will never go away. It's also lossless (when discounting colour depth).
The new formats are interesting webp, avif, JXL and so on.
Jpeg classic is the clear winner IMHO and will probably never be less relevant than the new fancier formats. JPG even does text and sharp edges, reds, and so on well if you tell your process to take into account chroma subsampling!
It's magic and it puts food on my table.
Gif is a weird one because it's silently been replaced while keeping the name around. Virtually every software using the term "gif" actually uses a h264/vp9 video with no sound.
Modern video formats are so much better that they are a no brainer to use while the word gif just got used to refer to looping video without sound rater than the literal gif image format.
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> PNG, the lossless format is great for diagrams and stuff with sharp edges.
But also, like GIF, it's pointless when lossless WebP exists and is supported everywhere. It's more efficient. Lossy WebP does not make as much sense though since jpegli entered the game.
OP has made https://halide.cx/iris/ which could make lossy WebP make sense, but it's not open source or generally available.
> The new formats are interesting webp, avif, JXL and so on.
WebP was introduced 15 years ago. New relative to JPEG perhaps, but certainly not new.
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Jpg, does not do text well, at its regular file size.And somewhat related it has no alpha channel.
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Gif is still there because it's still often the only option for frictionless video embedding. Embedded videos usually come with a video player that hardly ever quite works out well, often not starting automatically, not looping, or showing video player UI elementa that shouldnt be shown.
Jpeg LS do support lossless images.
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PNG was once (win98 era) the sparkling new format that nothing supported yet. Operating systems shouldn't waste their time supporting it.
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"These should just be vector images instead" is an argument made by someone who has never in their life attempted to create a vector image.
Also it would be nice to have a good standard vector format that isn't the complete kitchen-sink that is SVG, but we don't have that. We needed "jpeg but for vector graphics" and instead we got "html but for vector graphics".
So anybody saying "we should use more vectors" has to remember what the state of open vector graphics standards is.
In the context of the world it's all hair splitting, you can have a big photographic picture in png, or 1% compressed jpeg, or 1% jpeg converted to png. No new format can change it.
It seems to me that AV1 (the codec used in AVIF) has seen a lot more development in recent years, by virtue of being widely adopted for video. JPEG XL has not seen comparably massive adoption, perhaps owing in large part to Chrome rejecting it on dubious grounds (in spite of eagerly forcing the adoption of both WebP and AVIF earlier on). The pace of the reference implementation’s development has grown very slow, and most of the modest attention it’s been getting seems to have recently moved to the new Rust decoder, once the browsers finally made up their mind that’s what they wanted from the devs.
That considered, I don’t think it’s a fair comparison between the codecs. JPEG XL used to be far more impressive than AVIF; it’s great people (author included) have managed to push AVIF forward, but until similar efforts have been made for JPEG XL in earnest, I don’t feel like a comparison between their encoders says much about the codecs themselves. The author does take a guess on how much the JXL encoder could be improved, but that’s just that: a guess. It won’t be know until it’s been tried. And especially given the whole unfortunate history, I think JPEG XL really, really deserves a try.
It is getting its try, actively, in libjxl. People like to pretend AV1 got infinite resources; the reality is myself and one other contributor produced the vast majority of the image gains. I built Iris-WebP and aperture-alpha myself, from scratch. As a compression engineer, I think JXL is way, way harder to work with, and it would've taken me a lot longer. libjxl has community contributors, it is just an uphill battle with a codec like that. Same as WebP is an uphill battle due to its format restrictions.
> It is getting its try, actively, in libjxl.
That’s the thing, though: libjxl development hasn’t seemed all that active in recent years. The community contributors you mention seem quite far from driving the development, and some of them say that the usual devs have been busy with other projects (including jxl-rs as of recently).
> People like to pretend AV1 got infinite resources
I would not suggest that, but in another comment here you yourself say that SVT-AV1 (which you compare to JXL favourably in your article) has seen active involvement from ‘Meta, Netflix, Intel, independent contractors, and others’ – not to the community fork SVT-AV1-PSY and its successors contributing their improvements back upstream.
I can believe that JXL may very well be more difficult to work with, but am I wrong to assume you’ve been able to continuously focus on your own encoder (and apply your experiences from your earlier work on SVT-AV1)?
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Yes, but for speed which means a lot of SIMD plumbing, the larger workforce certainly benefited AV1 codecs!
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> It won’t be know until it’s been tried
We can reevaluate when and if improvements are made. The problem with statements like this, is its really easy to miss the showstoppers when imagining what something could be. All plans are amazing until you have to actually do them in the real world.
As the saying goes: Never fall in love with potential.
"We don't want to support another pile of security bug ridden C++ library" absolutely aren't "dubious grounds".
You'd rip a new one to Google if there would be a CVE in a new C++ library in Chrome because of it.
Now that Rust library is available, they will continue adoption, as it should be.
The stated reason for Chrome was not ‘we need a memory-safe implementation’. It was ‘there is not enough interest’ and ‘there is not enough improvement over AVIF’. At the time, there was interest and there was improvement over AVIF (which Google has decided to support regardless of memory safety, interest, or seemingly any deeper consideration).
Memory safety as a condition for adoption was brought up only years later, and by Mozilla rather than Google. The JPEG XL devs, who’d offered to work on it if there was interest, got to work as soon as interest was proclaimed. You might say it’s a good thing for Chrome to have held off adoption until then, but that’s completely incidental, not because they cared. Near-zero efforts to be fair and responsible were made.
> "We don't want to support another pile of security bug ridden C++ library" absolutely aren't "dubious grounds".
It is when that didn't stop them YOLO'ing in webp and then avif support.
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That JPEG XL prime computation is a pretty ugly DoS. Just selecting it in Finder, with the preview pane open, maxed out every core on my Mac inside a QuickLookSatellite that also ate 4GB of RAM while doing so - for a good 15 seconds. Not bad for a 2KB picture. It seems like Apple did not set sane limits on their JXL previewer.
It is, however, an incredibly cool demo of what the format is capable of. I'm not completely sure if an image format should be that flexible, but I'm impressed nonetheless.
When a format has so much flexibility, the world will glom onto the first thing that it solves and put it into the wild to solve that problem. The rest of the capabilities fall by the way side, yet not removed from the format. They're just ignored. MP4 can do so much more than the typical deliverable of a video stream and an audio stream. The spec allows for multiple video streams, multiple audio streams, subtitles, Flash like interactivity to allow self contained DVD style programming of menus to allow for chapter navigation, audio/sub selection, multiangle, etc.
MPEG4 supports interactive 3D scenes (read: games!) via bit-encoded VRML which can include JavaScript. I don't know any software which support this features (even without interactivity), but it is here.
I'd wrote reader for this bit encoding many years ago when company I'd been employed at made custom VRML engine for Samsung featurephones (project was dead on arrival as at this moment smartphones / Android become available and all this lineage of featurephones was killed).
> MP4 can do so much more
None of that has fallen by the wayside though? I have seen examples of all of those in the wild except for interactive menus and multiangle. Multiple video streams is incredibly rare to encounter but I have run into it a few times.
The argument in favor of flexibility (and jxl) is that if you optimize things for the "average" web user (as the essay seems to be suggesting) then fairly mundane usecases require you to start juggling formats, support becomes spotty, and things start breaking. It's nice to have generous limits within which you can be confident that things will "just work" for the end user. Even just on my own system I'd much rather use a single format rather than dealing with app x not supporting format y.
tl;dr jxl is the mp4 of image formats and that's exactly why I like it.
The only things I agree with the essay about are progressive decoding and decoding speed. Particularly the latter badly needs to be improved.
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I wonder if similar hacks apply to zlib and .png as well.
Zip and PNG bombs have been around for a while: https://github.com/0x48piraj/gz-bomb https://libpng.sourceforge.io/decompression_bombs.html
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Probably not; for PNG, the image size is declared in the header, so a decoder can decide immediately if it wants to decode the image or not. The output is bounded by the size of the image times the bit depth, and decompression runs in time proportional to output size. zlib bombs exist, but they don't affect png because a decoder can simply refuse to decompress past the size of the pixel buffer.
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The primary problem with that image is that is has over 60 channels, which means it'll take 20x more time to decode no matter what. Incidentally, the JXL spec suggests that web browsers shouldnt't decode images with so many layers. Jxl-rs will probably start enforcing such limits by default.
> I believe Web codecs should be purpose-built, efficient, and narrowly scoped to the needs of the Web.
The post downplays the usefulness of versatility. I disagree. I'd prefer not to play the "which image format is best for this image and this use case" game and having to transcode between them. For instance, it would be great if I could have an HTML gallery showing pictures of my files as I store them on harddisk. Today these are JPEG, because it's the lowest common denominator. WEBP, AVIF are not supported photography tools (e.g. https://support.captureone.com/hc/en-us/articles/36000262921...) and I don't expect support to ever be added since it is not formats intended for photography.
I got an impression JPEG XL is not a single format, but many formats put under one brand (same as webp), you still need to choose these formats and transcode between them.
JPEGXL is a single format, but when converting from other formats you can do it lossless or lossy, and optionally make it progressive.
Well, anything that supports JPEG XL will support all of them, so you can just re-use the files an the web as-are.
I personally find AVIF more versatile. I just throw images at it, and it does a great job. As the article identifies, JPEG XL performs worse than AVIF in general, but it's particularly bad at things like illustrations and screenshots. With AVIF I don't need to worry about that.
I've always found it annoying how most cameras only let you save their photos as some combination of JPG/PNG/HEIC/RAW, often without any adjustable quality settings or option to save several copies in different formats.
It would be great if their behavior could be customized in a more modern web-friendly way, like "Save the original photo as a 95% quality AVIF in this folder, and also as an 70% quality resized WebP in this other folder".
The camera's I've owned (Canon and, in more recent years, Olympus/OM System) all could do RAW, JPG, or RAW+JPG, or in some cases cRAW+JPG, with several quality settings available for the JPG side.
But remember, on a camera you're wanting to maximize battery life, image quality and certain key performance metrics. The OM-1 Mk II can burst up to 120fps of 20 megapixel images with locked focus or 50fps with continuous AF. Thats a huge amount of data to capture, process and write to media. I think we want cameras to optimize for that. It's trivial to dump the resulting files on your computer and then convert between formats to your hearts content.
Nobody has brought it up yet, but JPEG XL seems to be close in potential and flexibility to OpenEXR. It seems more a competitor to something like that--for use in image processing and digital art pipelines--than something like JPEG, WEBP, or PNG.
That said, I have converted my personal JPEGs to JPEG XL, because you can losslessly convert back and forth between the two for smaller filesize in JPEG XL with no quality loss, so I get free storage savings and can get the byte-for-byte original JPEG back if I need it.
I knew about the lossless JPEG to JPEG XL compression story before, but had no idea that it was a two-way road. That's truly f* impressive. Boggles my mind even more the fact this format hasn't been adopted widely yet.
JPEG is a lossy frequency-space compression stage followed by a lossless Huffman coding stage. The second stage is quite generic as such, essentially compressing a stream of bits.
So you can relatively easily replace the second stage with something better. And since it's lossless you can easily go back.
Dropbox[1] and others have exploited this for reducing storage requirements, converting back on-demand so the client doesn't notice.
https://github.com/dropbox/lepton
byte-for-byte identical file actually. Not just imagery. You can basically save 30% without loosing ANY bit of the original file
Because what you save in terms of storage, you pay for in decode time, which is an important consideration on the web.
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This blog post makes two incompatible arguments:
1) AVIF has now been radically improved to the point where it's actually quite good in ways that previously it was not.
2) JXL will not be improved despite the fact that the performance of every other codec has always radically improved over time.
Everything else aside, including a few clear methodological errors, it's ahistorical and unsightly to be unwilling to imagine that future implementation effort will accomplish anything. Some might call it hypocritical.
I invite you to re-read the post carefully, with the attention it deserves. Hint: at no point the blog post says JXL will not be improved.
It sounds like you don't recognize the relationship between text and subtext.
The entire post amounts to saying "JXL in its first iterations was better than AVIF's more advanced state of development and support, but AVIF very recently got better only after several years of widespread adoption, and I don't think JXL would too".
The arguments given against JXL cannot be reconciled with the history of codec development.
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This comment reads like you summarized the post and didn’t read it
Believe whatever you want. :shrug:
Note, that JPEG XL was added as a possible compression method for DNG files (Digital Negative - stores raw images with raw sensor data of a camera).
Because of it, for the past couple of years, all new iPhones and almost all Android phones (mostly Samsungs) already contain a JPEG XL encoder / decoder (to generate these DNGs).
I'm sure this is right about all the technical things, but the stuff about the requirements of a format for the web misses the mark IMO.
Normal people don't pick an image format based on whether it is suitable on the web or not. They want a format that works everywhere. If I download or upload a photo I don't want to have to do a lossy format conversion. If I'm writing an image processing tool it would be great if I can make it just support one input format that everyone uses, rather than "web" formats and "non-web" formats.
So I think a large part of the attraction of JXL is that it is a single format that works both for 10000x10000 lossless scientific images, and for 256x256 lossy web photos. You don't have to be an image format expert any more. Just always use JXL.
Definitely a shame about the technical flaws listed here though - especially decode time.
Professional web developers want to create a great experience for their users, so they go beyond simply serving whatever comes off a digital camera.
As the article identifies, JPEG XL is kinda bad at certain types of images, whereas AVIF does well across the board, so if you feel compelled to pick a single format to use, AVIF would be a better choice, but it's definitely worth optimising your web images for the web.
Also, JPEG XL is two codecs bundled into one, VarDCT and Modular. So, even if you're picking JPEG XL as "the one codec", you're actually picking two, and you need to choose between them at encode time.
> Also, JPEG XL is two codecs bundled into one,
That's an internal detail that doesn't really matter to anyone outside library implementors, or when you're choosing encode settings though.
It's the same in Opus. Technically it's two formats, but as long as they're one entity that's either supported or not supported, everything is good.
AVIF does seem to have at least a couple of downsides compared to JXL like max 12-bit depth, no JPEG reencode and worse recompression stability. I think they probably could have added those though, and then we wouldn't have yet another format to support for eternity. Oh well, they had their chance.
Much like WEBP, JPEG-XL is two different codecs in one. There's VARDCT mode, and Modular Mode. Modular Mode is normally used for lossless, but it can also be used for lossy as well. When you use Lossy Modular Mode, you get different kinds of compression artifacts than what you'd see in a JPEG file.
For Lossless: JPEG-XL wins, then WEBP, then PNG. (Sometimes lossless WEBP wins)
For Lossy: AVIF wins, then JPEG-XL, then WEBP, then JPEG.
Lossy Modular isn't efficient enough to compete with even JPEG.
Also, look at the graphs – Iris-WebP beats JPEG XL.
Sorry for the dumb question, but I don't understand something in these graphs. Since it's x=speed and y=bd-r, is this test done at a fixed target quality/size?
JpegXL progressive decode is way better than AVIF:
- it's first image is way earlier: 2KB vs 8KB
- from 8KB to 100KB it's blurrier than AVIF, but it's more pleasing to look at and less blocky than AVIF. I highly prefer it.
- from 100KB until finished 288KB it's actually ~4x sharper than AVIF
Overall JpegXL gives the much nicer experience.
^ tested with pokebowl (https://jpegxl.info/resources/progressive-loading-demo.html)
I feel like JPEG XL could be a good RAW format for mirrorless cameras... something with huge flexibility but with the perk of being easier to view casually on other devices. And then that in turn could make it a more useful web format? Camera vendors are of course notoriously proprietary/stubborn.
Just demosaiced JPEG XL? That's not raw.
Lossless JPEG XL is in the DNG spec since three years (v1.7). So, you can convert your proprietary camera raw files to smaller ISO standard compliant JPEG XL compressed DNG raw files (mosaiced, not linearized).
PureRAW can now output linear DNG's compressed with JXL. It's amazing the first time you use it seeing 25mb RAW files go in, get made linear, and pop out 8mb or 9mb, then toss them in your RAW developer of choice and still find all the dynamic range and such you'd expect from the original RAW. I'd been doing that on my own with a script that called Adobe's DNG Converter, which has the same capability, to convert older versions of PureRAW's linear DNG to JXL-based DNG files, but that's no longer necessary.
Unfortunately, at least as of perhaps a year ago, I couldn't find any other actively maintained software tooling that could reliably do what Adobe's DNG Converter was doing, and there's so much nuance to the world of RAW files that's not at all just a trivial one-shot prompt to Claude/Codex to roll your own.
> not linearized
Not linearized as in samples do not represent linear color space? I think that's untrue, as all sensor work I've done (a decent amount across many projects) are linear: double light = double photon count = 1 bit of sensor space. There are technically often some bends from physical and engineering effects (photon interaction with substrate has some variability, temperature affects things a bit).
Or is there some other meaning of "not linear" you mean?
Raw isn’t an image though, it’s pre-image. And we have an open raw format already. DNF I think. With pretty decent adoption.
You are thinking of DNG which is more of a container format. It can use multiple image formats internally to record the actual image, one of them being JPEG-XL.
iPhone raw images are actually a jpeg xl inside the DNG.
True. I would love to have lossless images (and video) out of my devices still. Not as a replacement for RAW but as a middle ground between RAW and lossy JPEG.
Not for quality reasons primaily but because keeping the first stages of the processing pipeline and the archival branch lossless solves some headaches.
it's even flexible enough to represent images pre de-bayering
I think, whole idea of «web images» is silly now.
Browsers are new OSes.
There is no any «web» anymore. E-mail clients are web, news readers are web, image galleries are web, heck, even image editing software could be web (google:photopea).
And as such there should not be «web-optimized» formats anymore.
"Web optimised" really means "internet transfer optimised". Eg, the benefits would also be there for native apps that are downloading images from the internet, and they're not the web.
In practice "web optimized" is a soft copyright control where the image is read-only to the extent the only readily available software that can open it is a web browser.
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> and narrowly scoped to the needs of the Web
> it was hard enough to get widespread WebP adoption
That's not a coincidence! And because these newer codecs are better outside the Web, it's not really "the same hill"
In the post, I say "I think WebP was a bit too narrowly scoped"
This is not a coincidence, but I don't think it was that devs looked at WebP and thought "huh, the lack of 4:4:4 and 10-bit support makes this less compelling for our product despite being all over the internet" – I think it was just a matter of not keeping up. Except for Apple, not sure why they took so long to implement it.
Wasn’t WebP pushed pretty hard by Google for several years, until the (ever shrinking) rest of the ecosystem sort of caved in? My impression was that there wasn’t much interest until it became more or less inevitable because of that.
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Can whatever the next new image format for the web will be please have a JSON block at the start giving
And it doesn't have to be JSON, as long as it's in a fixed location (looking at you, AVIF and JPEG), extensible and can be decoded by just reading the first 8KB or 16KB.
Then any future image format is a simple drop-in without requiring complex processing on the server side or a lot of complexity in HTML (not to mention CSS)
I'm the author if anyone has questions – AMA
How ergonomic are the modern AVIF encoders? I like libjxl (and cjpegli) because they are really good at generating reasonably compact, high-quality images.
For every other image encoder I used I couldn't find one setting that would make compact, high-quality images across the gamut of inputs (e.g. things like comics that have extremely visible high-frequency content would look terrible at quality settings that looked good for many photographs).
Have you tried the latest AVIF encoder? It's quality setting seems much more stable.
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Lossless was discounted due to webp, but doesn't webp lossless only use 8bit depth RGB? (I think it is important to have a separate file extension for lossless stuff anyway, otherwise it gets confusing quickly)
Lossless was discounted because lossless just isn't very useful on the Web
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I have a lot of basic questions about the CVVDP graph. Is the X axis encoding or decoding speed? Is higher better on the Y axis? What format is Aperture? I assume "aom" is AV1 but it wouldn't hurt to document it.
x-axis is encoding speed, Y-axis is BD-rate where higher is better. aperture-alpha is an upcoming encoder from Halide Compression, no more details than that. libaom and SVT-AV1 are both for AVIF; libaom is the AV1 reference encoder.
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We have to apply some weight to the fact that one is open, one isn't, right?
EDIT: Oh! Of course. AVIF is based on AV1. For some reason I was thinking HEIF the entire time I was reading the article. Man... withdrawn!
Really good read, btw. Very good points.
AVIF is royalty-free, & SVT-AV1 and libaom are open source.
Edit: saw you corrected. Much appreciated!
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AVIF _is_ AV1 in the HEIF container.
(.heif is sometimes used as a file extension generically, but HEIF is itself a container that can support various payloads.)
Both are open I think.
What do you think about the fact that most perceptual quality improvements in SVT-AV1 have been almost only driven by external, non-paid enthusiasts such as yourself while the maintainers have been basically only targeting VoD and RTC?
Compared to JXL (which admittedly has almost nobody working on except veluca these days...) which was focused on it since the beginning, I think it really matters.
I would argue that even if JPEG XL isn't the best choice for Web images, if browsers don't support it then that will widely hinder its adoption for its non-Web use cases. Would you agree?
The scenario I'm thinking of is sending a photograph by email. Let's say Sally has just had her second baby, and wants to send baby pictures to her mother, the baby's grandmother. Neither Sally nor her mother are computer professionals, and they don't want to care about image formats. Sally wants to upload a file from her camera, attach it to an email, and send it. Her mother wants to click on the email and see pictures of her new grandchild. Neither one of them wants to have to convert the image themselves.
Let's say it's a few years in the future and Sally's camera produces JPEG XL files by default. (Which I don't think would happen if browsers didn't support it, for exactly the reason I'm about to articulate). If Sally's mother's browser doesn't support displaying JPEG XL, then although Sally (who uses a different browser than her mother) sees the picture in the email when she sends it, her mother writes back an email saying "the picture didn't show up, can you resend it?" And they spend a few back-and-forth emails before finally getting tech support from a friend who helps Sally convert the picture to old-school JPEG so her mother can see it.
If that's the experience for end-users, cameras would hesitate to switch to JPEG XL as a default format. Because nobody wants a hostile review from a user saying "My mother couldn't load my baby pictures, what kind of lousy camera are you making?"
So even if it's not the best format for the Web, I'm still persuaded that having universal browser support for a format intended for photos is an important factor, and devices like cameras will not switch to it as a default format until manufacturers are certain that browser support (and OS support, and electronic photo frame support, and so on) is nearly universal.
None of that takes away from the argument "Other image formats are better for saving space on the Web", which is the main thrust of your post. But I do disagree with the last line, "I'm just not personally convinced we need it in browsers any time soon." I believe that if browser adoption is lacking, adoption of the format in places where it makes lots of sense (like cameras) will also be slow.
What are your thoughts on that argument?
> I would argue that even if JPEG XL isn't the best choice for Web images, if browsers don't support it then that will widely hinder its adoption for its non-Web use cases.
Both Firefox and Chrome [1] have committed to shipping JPEG XL later this year. Safari has supported JPEG XL since 2023, though their implementation doesn't support progressive images yet.
So the major web browsers will support JPEG XL later this fall.
[1]: "Intent to Ship: JPEG XL" - https://hacks.mozilla.org/2026/08/intent-to-ship-jpeg-xl/
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> But I do disagree with the last line, "I'm just not personally convinced we need it in browsers any time soon." I believe that if browser adoption is lacking, adoption of the format in places where it makes lots of sense (like cameras) will also be slow.
I'm not even personally convinced it is useful for cameras. Sally's situation isn't particularly bandwidth or feature-constrained, so JPEG or PNG work. Maybe JXL is solving problems that don't exist?
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What do you think the best use cases for jxl are? Where does it still have an advantage over other formats?
I think it is a potentially good camera format, good medical & scientific imaging format, good RAW compression format (Apple uses it in some newer iPhones for this), good media interchange formats for tools like Photoshop (think about storing all of your layers inside of one JPEG XL that's fully compatible with .psd files), and more. It is incredibly expressive and versatile, which is what makes it so risky on the Web.
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Thank you for an interesting article. You’ve helped AV1 come a long way!
In the ‘Lossy Compression Efficiency’ section, you compare the codecs using various metrics, but I don’t think you say anywhere what quality the images were encoded for. Did you forget to mention that or am I just reading things wrong?
(I assume BD-rate tells us how similar the images look, but I also assume the values would change if the encoders were made to target different qualities, hence why the intended quality seems quite important to know.)
It would be nice to see the actual R-D curves for the codecs instead of compressing them into a single number. Also, what is BD-rate computed with respect to, jpegli at p0?
Very compelling and thoughtfully written article. Thank you!
What about the current AV1 patent issues, like Sisvel/Access Advance and Dolby vs Snap? Does that change the AVIF vs JXL comparison at all?
those issues aren't real. they're nuicense suits by a patent troll. a couple companies will settle cause it's easier and cheaper, but if they ever try to go after someone big they'll fight it and get the patents invalidated for covering 30 year old work
What format would you recommend for archiving photos if I don’t mind slight quality loss?
I like how every time we have a codec fight no one seems to care very much about how long it takes to encode these files. Like I get it, the amortization schedule often works out, but there are scenarios where images need to be generated dynamically and will only ever be downloaded once.
It's very hard to beat the encoding performance of libjpegturbo, even with an asic.
Encoding time is one of the things that JPEG XL has claimed over AVIF for years, but in the latest encoders, it doesn't seem to be the case.
> It's very hard to beat the encoding performance of libjpegturbo, even with an asic.
Pretty much any platform with a hardware jpeg encoder beats libjpegturbo. So probably all smart phones, large scale CPUs, even tiny few $ microcontrollers like ESP32's have hardware encode/decode that outperforms libjpegturbo.
Sure, if you ignore PQ completely.
Not that libjpeg-turbo is pinnacle of quality but hardware encoders, seriously?
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> there are scenarios where images need to be generated dynamically and will only ever be downloaded once
Those scenario amount to epsilon percent of scenarios, though, so it makes sense to ignore them most of the time.
I kind of settled on avif. I am not at all implying avif is perfect, in particular at high compression I notice the quality isn't quite as good as often advertised. For similar size compared to jpeg, avif is divine; and I also found avid better than webp in my own tests, so I switched to it. I don't quite see JPEG XL being really significantly better though. I think a really big problem here, even aside from Google trying to force deadlock people into its evil monopoly structure, is that we have competing formats (avif, jpeg-xl, webp) and that's IMO not so great when we want to have "one format to rule them all" that's better than jpg or png or gif. JPEG-XL is kind of a late starter here; if it is not really significantly better than avif or webp then I do not see it will gain any real foothold in the coming years.
If JPEG XL doesn’t become useful on the web, is it really likely to become popular with camera manufacturers, professional image editing tools, etc?
What does it offer there that existing workflows can’t support? Do those advantages make up for the transcoding that every web publisher would need to do to make the outputs useful on the web?
> If JPEG XL doesn’t become useful on the web, is it really likely to become popular with camera manufacturers, professional image editing tools, etc?
I suspect that eventually, the browser makers that are reluctant to add JpegXL support will do so, even if reluctantly, and so it will eventually "become useful on the web".
The reason why is Adobe added JpegXL as a compression format for PDF's, and as every browser maker wants their browser to also be a "PDF viewer", this means they must include a JpegXL decoder to be able to support PDF's going forward. If they must have a JpegXL decoder anyway, it is not that difficult to also add it as another supported format for the <img> tag.
Looking forward to a future where we can arbitrarily DoS anyone with a PDF that computes massive swaths of prime numbers.
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Most people using dedicated cameras shoot in RAW, then use a program to process and export the photos afterwards. So camera manufacturer buy-in isn't super important.
I've been exporting in JXL from Lightroom for a little while now, you get slightly smaller image sizes and HDR with no real downsides. On the web I imagine this will translate to higher quality images on social media since platforms can get more out of the same file size. It will also likely be the end of HEIF which is a pain to deal with due to patents.
The second paragraph doesn’t follow from my question, because it assumes JPEG XL does become useful on the web. The author believes AVIF is too far ahead already.
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DNG added JPEG-XL as a format for both raw and compressed recently
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I’ve been shooting with semipro to pro cameras for decades across brands, and I haven’t came across a single camera that supports shooting JPEG XL.
HEIF is what is getting support in recent models; but JPEG still rules supreme for its compatibility.
Web publishers should definitely be stripping metadata at least, and transcoding isn't much harder. For anyone who cares about bandwidth, transcoding to efficient formats is non-negotiable; if you don't, then why do anything? Just ship PNG, who cares?
I think one of the compelling use cases for camera manufacturers would be an interoperable format for editors. Since JXL has support for so many channels, you could load your image into an editor, edit it, add layers, etc., and export as JXL, which could be used for other things.
> Web publishers should definitely be stripping metadata at least
No, they shouldn't. Not blindly. Metadata can include copyright license information, such that stripping it violates the license to reproduce the image.
iPhones have been using it for its ProRAW format since 2024.
It has 3 options:
JPEG Lossless (most compatible)
JPEG-XL Losless
JPEG-XL Lossy
> Progressive rendering (which AVIF supports) decodes a low-fidelity rendition before the full image arrives. AVIF didn't support progressive rendering for a while, and during that time I believe it was deeply oversold. Now that libavif has implemented it (it was always possible), the conversation appears to be over.
This is false. AVIF does not support progressive decoding/rendering. What the author is referring to here is image layering. A lower resolution image layered below the full resolution image, which is loaded and rendered first. That is not progressive decoding/rendering. It is a thumbnail.
Unlike AVIF's false advertising, JXL truly supports progressive decoding/rendering. With JXL, you do not first load a thumbnail before loading the actual image. The lower-quality image that JXL shows while decoding is derived from the data of the actual, full-resolution image.
> A lower resolution image layered below the full resolution image, which is loaded and rendered first.
I'm curious, where did you learn progressive AVIF works like this? Have you actually read the spec, or does your understanding comes from somewhere/someone else and never challenged the truthfulness of it? Progressive AVIF is truly "progressive" -- it never involves "loading a thumbnail" or "layering an image over another".
In reality, each pass (up to 4) can refine previous ones (thanks to AV1's inter-encoding toolset), avoiding storing redundant information between passes. The viewing environment doesn't need to render a given pass if a subsequent one has already been downloaded. Finally, scaling is configurable -- you can have your first pass already be at full res, just at a lower quality.
Hope this helps clarify how progressive AVIF actually works under the hood.
> A lower resolution image layered below the full resolution image, which is loaded and rendered first.
Unlike a thumbnail, higher-resolution layers can be predicted from the lower-resolution layer, so those bits are not wasted. That is not possible by layering <img> elements.
You're wrong. AVIF does support spatial layering where the full-resolution image is derived from the lower-resolution layer, and cannot be decoded independently.
Yes, the format is not inherently progressive. But having the fine steps in progressive quality that JPEG-2000 and JPEG-XL have has less general usefulness than the amount of words complaining about it.
Jpeg2000 (and jpeg ls and jpeg xr) thankfully wasn’t implemented in any major way. Keep it simple, stupid.
Can a similar technique be employed in JPEG XL, or does the format not allow for it in any way?
Not sure if the difference is materially relevant to UX at all. JPEG XL achieves progressive rendering at a great cost to its selection of coding tools, so I side with AVIF's approach.
Does the difference matter?
Yes, if you look at the demo, the "progressive" AVIF loads a visible image at 8.5KB, and at that point, it looks better than the progressive JXL. However, that is ALL the AVIF shows until the image has fully loaded. At around 98KB, the JXL looks significantly better, and at around 240KB already looks really close to the final image, while the AVIF still looks terrible. At 280KB when the AVIF finally loads, they look identical.
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Progressive rendering is just a different way to layout the pixel data. Embedding a thumbnail is storing two distinct images. In other words, progressive rendering should be more efficient space and bandwidth-wise.
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Of course it does, with one you have to render twice and store two layers which costs you both compute and storage. With the other you can just take the image mid decode at a point and display it. Single decode operation, no layer mess.
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The difference matters, as it means that AVIF's "progressive decoding" serves no technical benefit and is only a minor ergonomic benefit: On a website, you could achieve the same effect simply by layering two <img> elements on top of each other, one with the thumbnail and one with the final image.
If layering to <img> elements is fine for your use case, then it simply means you have no need for progressive decoding.
How does progressive rendering actually that most OS GUIS are not multithreaded ?
The preview in finder is still going to block. Im saying this as a MAC user speaking of experience browsing mounted drives that sometimes are slow and it feels like the window freezes up.
Thumbnailing happens in a background process and shouldn’t block the main thread; rather hangs are usually because fetching xattr over SMB is slow and Finder will block until it’s enumerated the metadata of every file in a folder.
Preview actually does use progressive rendering for large enough images, even from SSDs. You can tell because opening an image will be blurry for several seconds, even when the full size image could have been decoded in a quarter second or less.
Progressive rendering is intended for the Web and it does work.
We all know these aren't purely technical reasons, it's to break the monopoly of one Internet Company's decoder format portfolio. You can't let one Fruit Company's format be the thing either, so it's basically a L for engineering but a W for pleasing everyone TBF.
AVIF is royalty-free, with open-source implementations not developed by Google. Google's implementation is libaom; as you can see, SVT-AV1 beats it. SVT-AV1 is developed by a number of companies – historically Meta, Netflix, Intel, independent contractors, and others. I worked on SVT-AV1 myself. I don't see how this is a bad thing for everyone, even if Google drove standardization of AV1?
There were something like 40 companies involved in AV1 standardization. Quite a few technical contributions did not come from Google, and quite a few of Google's proposals were substantially modified by feedback from others before they were included (and not all of them were eventually included).
Source: I lead Mozilla's technical contributions to AV1.
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> You can't let one Fruit Company's format be the thing either, so it's basically a L for engineering but a W for pleasing everyone TBF.
What exactly is "Fruit Company's format"?
I'm guessing HEIC.
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Had a lot of the content in this article came out 4 years ago I would have agreed. At least we finally don't have a fake Image Coding Comparisons [1] that tries to undermine JXL.
Ignoring AOM and AV1, I was the first few on HN apart from its author supporting JXL from the start, I would argue the biggest case against JPEG XL is JPEG li.
Jpegli offer enough quality improvement and advantage without introducing an entirely new codec. And all of a sudden the bar for next image codec now needs to be even higher.
[1] https://storage.googleapis.com/avif-comparison/index.html
> only roughly 11.9% smaller than lossless WebP anyway
That’s huge, no?
The chart showing jxl-rs taking 1209ms to decode a 5456x3632 image in a single thread is a little damning, but is there an equivalent benchmark showing multithreaded decode performance? Clients tend to have an abundance of threads these days.
Something is fishy here.
The JPEG XL report [1] measured between 240-270 Megapixels/s on 6 cores using the C++ implementation (disclosure: I was responsible for its SIMD/threading), about twice as fast as the then-current libaom.
Measuring on a single core is deeply misleading because our code was designed to scale well. I believe AVIF requires tiling in order to parallelize, which causes artifacts at tile boundaries.
[1]: https://arxiv.org/pdf/2506.05987
It’s a measurement error: the `hyperfine` command uses `jxl_cli --speedtest` which, by default, does a warmup run that ends up in hyperfine’s measured time.
jxl-rs is single threaded. It may be not a good idea to use many threads per image as one page can have many images.
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The time would be less, but you still need to power those cores. Single thread performance can be a good indicator of what it'll do the battery on your phone.
Not at all.
CPU power is proportional to frequency^2. Running on 4-6 little/efficiency cores (which are widespread on mobile) is likely faster than one big core, and uses less energy.
jxl-rs is a relatively new implementation, not yet optimised for speed. It’s hard to say how much faster it’ll get, but I assume it would at least get near libjxl’s level.
These sorts of things always talk about progressive rendering. Who actually likes progressive decoding? Like...what year is it?
I don't want an image to appear in any form until its loaded. I never need to see a blurry placeholder, and there is zero value in that even with bad connections, but the situation is farcical when everyone has ultra-fast connections everywhere.
This is similar to pages that use custom fonts but will happily show the text as quickly as it can, and then suddenly restyle/relayout the page when the custom font loads (Flash of Unstyled Text - FOUT). It looks terrible and is jarring. Progressive rendered images are the same.
I disagree with this. If I'm in a poor connectivity situation, a preview can help me quickly decide if an image is worth waiting for.
I'm not talking about blurhash here - those are 'cute' at best. I'm talking about previews that let me determine the subject of an image.
I was on a train recently and an image preview X delivered to me was enough for me to tell that the image was a particular meme format, and thanks to context, I knew enough about the image, and didn't bother waiting for it to load.
You've left some 36 comments on this submission (which is honestly weird as HN usually rate limits to avoid that sort of aggressive participation), and your comments seem extremely...cherry picked. In another comment you dismissed the bandwidth savings of JXL because connections are so fast that eh, who cares, and in this case you herald the importance of progressive rendering because connections are so slow.
Are you the author of the submission? Literally never seen someone so motivated in a conversation before.
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I wasn't really sold on the argument initially, given they admit there's some real lossless usecases, but this is a good bit from the conclusion:
> Not to mention an additional compatibility headache now exists for anyone just trying to download an image from the Internet and use it somewhere – it was hard enough to get widespread WebP adoption, and I don't think it's worth doubling the pain by having to climb the same hill for AVIF and JPEG XL. Especially when JPEG XL doesn't appear to add anything to the Web platform.
It is very annoying downloading an image for the web and then trying to upload it somewhere else also on the web during these transition periods.
There exist lossless use cases, for sure. I think most people would be well-served by high-fidelity lossy that saves a lot of bits while still looking perceptually identical. Whoever isn't served by that most likely doesn't care about size savings, and can stick with lossless PNG.
The problem with that is that the idea many stakeholders (especially big platforms) have of "perceptually lossless" is actually compressed to hell garbage. The only way you as a user can ever guarantee actually perceptually lossless is to use a fully lossless format.
I didn't realize progressive AVIF was a thing recently either; the comparison between that and jxl was pretty surprising.
Worth noting that this progressive AVIF, when viewed in Chrome, has only two states: a "base layer" which pops in around 8KB, and the full image which appears 270KB later. The comparison JXL continues to refine during most of the download, so it winds up looking substantially better than the AVIF at around 95KB loaded, and looks pretty good (almost as good as the full 280KB AVIF) by 175KB. I suspect that there are a lot of knobs to turn for both progressive modes, but this particular case could definitely be cherry-picked to favour either codec.
Progressive AVIF is very flexible: it supports up to four passes, at configurable quality and dimension scaling levels. You can have any given pass reference up to two previous ones for refinement (thanks to AV1's strong inter-encoding capabilities), and you add filters to non-final passes (like blurring) to achieve a desired loading aesthetic.
That JXL page happens to use two passes, but the knobs are there to customize the experience to fit the use case.
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I believe wholeheartedly that AVIF's approach is significantly better UX.
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Perhaps it's just a bad example. I suppose avif can support multiple "scans" of progressive encoding as well.
Hello everyone.
Because of Gianni's great post, I've decided to go full throttle on rewriting and finally publishing the JXL vs AVIF post after deciding to partially shelve it last year.
This should be especially interesting looking at the differences between my testing and Gianni's.
Is there a way to have fast on-the-fly WebP encoding? When i checked it, it was unusably slow (multiple seconds for large images), but maybe that was the implementation. That alone made JXL far more interesting to us.
The form of JPEG-XL that can lossless convert to/from traditional JPEG is exciting tech that should be adopted universally. The non-backwards-compatible version of it seems redundant with AVIF.
Author entirely misses the case for what many people want it - re-compressing old JPEGs that they have no better sources for into JPEG XL with out decode-encode loss
The author covers it:
> JPEG recompression is the ability to losslessly re-encode JPEGs as JXL images while saving bits; the oft-cited number is 20% savings. However, the user pays for this in decode time, as recompressed JPEGs take ~33% longer to decode
TIL that AVIF supports progressive decoding, cool!
I guess we found the tenth dentist.
"but strong mode-decision pipelines can pick the right mode for the job and save lots of bits" - citation needed. just a bit above author claims lossless is not useful for web, disregards modular jxl that uses nearby pixel predictors (even though it can be lossy, too), then produces this claim against vardct. spoiler - dct frequencies ARE using "nearby pixel values"
really strange article.
I would argue that as of 2026, we have enough storage and bandwidth that lossless compression is justifiable in almost every use case.
Computers should not be making images look worse than they were captured. It's not 1996 anymore. We don't need to be doing this at all.
Depends on your location. While I have a decent internet connection at home, the mobile one is trash. Good for IM and not much else.
Most of the people I know only have the mobile connection, pay a lot for the privilege, and while speeds are generally good (LTE and up), the monthly cap for almost all of them is 10-20 GB.
Just to put some numbers to this, I looked at an image I recently took with my phone:
Original image (JPEG): 3072×4080, 2.6 MB. Transcoded to JPEG XL: 2.1 MB.
To display at 2x density on my web page, it would be 1598×2122.
Lossless JPEG XL: 2.5 MB. Web-quality JPEG XL: 93 kB. Web-quality AVIF: 70 kB.
It still seems worth it.
A 2.5 MB download just isn't a problem in 2026. I would far rather see the lossless image than save a few MB.
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All my photos are HEIC. Why not just use what I have and not translate?
HEIC has a very messy patent situation around it which limits what tools work with it.
E.g. for official Windows support by Microsoft you need to buy the codec from the Microsoft App Store for $0.99
Formats that aim to be web standards should try not to be patent encumbered. There was a lesson to be learned from the Unisys debacle in the 1990s. If you don't want to reencode for the web, use a device that captures in a format that can be shared on the web.
You should never transcode lossy source files because there is generation loss in quality.
There is still a lot of reason for Apple to switch from HEIC to JXL for photos going forward since HEIC is patent encumbered so it will never see widespread use.
Well, JpegXL does have one really cool feature: you can transcode jpeg to jpegxl (and back) losslessly. For jpeg to jpegxl it'll save something like 15-20% in size.
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Because you'll be hounded by patent pools and sued into oblivion if you dare to use it in your own software and aren't Apple, Microsoft or Samsung.
Think about how many images large platforms deliver every day, and the benefits of saving bits on each of them.
No wukkas, JPEG XL support in Chrome ships by the EOM \o/
Rather than AVIF or JPEG XL or WebP or HEIF or any of that stuff, my actual ideal choice that I wish everyone used is just good ol' JFIF. I like that I can take a file downloaded from the modern Web and open it on my '90s and 2000s computers. I emphatically do not care that it's some marginal percentage “““more efficient””” — more efficient for Google and Apple and Amazon and all the other silo providers who are moving more data every day than I will produce in my entire life. But why should I have to suffer backwards-incompatibility for their sake?
Backwards compatibility is cool; stop the fucking churn! I have done this just within this past week, in fact, when I moved a JPG over to my Mac OS 7.6.1 machine (PowerBook 2400c!) to use as a new desktop wallpaper†.
† Via Décor https://macintoshgarden.org/apps/decor
Interesting.
> This rules out JPEG XL's lossless advantage, which in practice is only roughly 11.9% smaller than lossless WebP anyway
> It cannot be worth bringing a new image codec to browsers to save 12%
What? 12% is huge.
Yes but the decode time is orders of magnitude more.
who cares, you're not displaying 60 of them per second
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Lossless dismissed? 11% isn't nothing, that's trillions of images out there. Mozilla's own data shows JXL lossless beating AVIF and WebP. That's the one weakness of avif that bothers me, for lossy and speed it is brilliant. Companies may have another itch with the misleading licensing:
AVIF's "royalty-free" is under active legal attack (Dolby v. Snapchat). JXL has clean ISO commitments so no such suit would be possible. If "free" matters, JXL is safer.
Perceptive quality with the latest AV1 caught up, but that's a rigged timeline. Chrome supported JXL "late", then pulled it altogether. AVIF did improve further yes, it had web usage, it was behind when the race was meant to start. Why would JXL continue to optimize for web once the major browser refuses to support it.
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I agree that the choice for JPEG XL is mostly politically motivated: it isn't Google. And its name is derived from JPEG, which is an IETF standard which gives it more clout.
>it isn't Google.
It is Google. The JPEG XL standard evolved from a codec Google made, Google was involved in the standardization process, and Google heavily contributed to the reference implementation of JPEG XL.
https://ds.jpeg.org/whitepapers/jpeg-xl-whitepaper.pdf
Yes, but unlike WebP it wasn't exclusively designed and developed by Google. That's a big difference.
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And Google also removed jxl support in Chrome in '22 (only to put it back in recently)
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JPEG isn’t from IETF.