Comment by Sardtok
6 hours ago
Have you heard of EDN? It's mostly used in Clojure and ClojureScript, as it is to Clojure what JSON is to JS.
If you need custom data types, you can use tagged elements, but that requires you to have functions registered to convert the data type to/from representable values (often strings).
It natively supports quite a bit more than JSON does, without writing custom data readers/writers.
Another thing to possibly consider would be ASN.1 (you can also use the nonstandard extensions that I made up, called ASN.1X, if you want some of the additional types I included such as a key/value list). (You are not required to implement or use all of the types or other features of ASN.1 in your programs; only use the parts that you use for your specific application.) Unlike EDN, ASN.1 has a proper byte string type, it is not limited to Unicode, it has a clearly defined canonical form (DER, which is probably the best format (and is the format used by X.509 certificates); BER is too messy), etc. DER is a binary format (and the consistent framing of different types in DER makes it easier to implement and work with than the formats that use inconsistent framing, although that also makes it less compact); I made up a text format called TER, which is intended to be converted to DER.
I haven't, but it's an interesting format for sure.
I've found a more comprehensive documentation here. [1]
At first glance, I would say it's a bit more complex that it should for a "human readable" format.
[1] https://edn-format.dev/