Google announced it has begun testing FLoC, Federated Learning of Cohorts, in Chrome. Specifically the FLoC origin trial in Chrome 89 will work on websites that don't opt out of it.
Google said "a new piece of web technology - Federated Learning of Cohorts (FLoC) - will start to roll out as a developer origin trial in Chrome. Keeping in mind the importance of "and," FLoC is a new approach to interest-based advertising that both improves privacy and gives publishers a tool they need for viable advertising business models. FLoC is still in development and we expect it to evolve based on input from the web community and learnings from this initial trial."
You can register into this trial over here if you want. Provides callers (primarily ad-tech) with a "cohort label" shared by thousands of people with similar browsing habits to aid in interest-based online advertising. The browser will group people together into k-anonymous interest cohorts via purely on-device computation, and reveal the user's cohort via script. This is available on Chrome 89 to 91 and the trial ends on July 13, 2021.
There are more details on how this works over here.
Google said that the initial testing of FLoC is taking place with a small percentage of users in Australia, Brazil, Canada, India, Indonesia, Japan, Mexico, New Zealand, Philippines and the U.S. Google said it will expand to other regions as the trial expands globally. If you’ve chosen to block third-party cookies with the current version of Chrome, you won’t be included in these origin trials. In April, Google said it will introduce a control in Chrome Settings that you can use to opt out of inclusion in FLoC and other Privacy Sandbox proposals.
Forum discussion at WebmasterWorld.