The EFF on FLoC, Google's plan for browsers to aggregate your browsing habits and make them public for ad-personalization: https://www.eff.org/deeplinks/2021/03/googles-floc-terrible-idea. Short summary: it's a bad idea and if you care about privacy you should switch to a non-Chrome browser.
Technical summary: it's based on k-anonymity (https://en.wikipedia.org/wiki/K-anonymity), known as inadequate at protecting individual privacy in social networks (https://doi.org/10.1109/CASoN.2010.139). If you use Chrome, assume all bad guys on the web can see all your browsing.
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