Comment by troupo
3 years ago
Your description claims that Google sends topics to site X only from history related to site X.
Which makes this useless from advertising point of view. Which also means that Google is using the whole history to come up with "rough tooics".
Let's see:
--- start quote ---
With Topics, your browser determines a handful of topics, like “Fitness” or “Travel & Transportation,” that represent your top interests for that week based on your browsing history.
https://blog.google/products/chrome/get-know-new-topics-api-...
The browser observes and records topics that appear to be of interest to the user, based on their browsing activity.
https://developer.chrome.com/blog/new-in-chrome-115/
With the Topics API, the browser observes and records topics that appear to be of interest to the user, based on their browsing activity. This information is recorded on the user's device.
https://developer.chrome.com/docs/privacy-sandbox/topics/ove...
--- end quote ---
From your last link:
> API callers only receive topics they've observed
> A design goal of the Topics API is to enable interest-based advertising without sharing information with more entities than is currently possible with third-party cookies. The Topics API is designed so topics can only be returned for API callers that have already observed them, within a limited timeframe. An API caller is said to have observed a topic for a user if it has called the document.browsingTopics() method in code included on a site that the Topics API has mapped to that topic.
This doesn't say that topics only come from the same website. It only says that if a website has "observed" any of the thousand or so topics, one will be provided to that site based on user activity.
Edit. Literally last link:
> Map browser activity to topics of interest. With the current design of the Topics API, topics are inferred from the hostnames of pages the user visits.
That sentence is about how the Topics API finds topics, not about who the topics are shared with.
4 replies →
The top 5 topics for an epoch is calculated using all of your browsing history in that epoch.
A site observing a topic in the last 3 epochs unlocks the ability for document.browsingTopics() to return that topic from your top 5.
Every epoch each site has a 95% chance to be assigned 1 topic out of your top 5 topics and a 5% chance that it is assigned a random topic. When browsingTopics is called it gets the topics it was assigned for the last 3 epochs. Real topics are not returned if the site did not observe that topic in the last 3 epochs as mentioned in the previous paragraph.
It's on a per-tracker basis. For an ad provider to see a given topic it must have been embedded in a site with that topic. In GP's comment "site X" is referring the site being embedded, not the top-level site. Again, this is reducible to third-party cookies.