Google started blocking third-party cookies for 1% of Chrome users (nearly 30 million people) on January 4th, 2024. It'll gradually ramp this up to the rest of the 99% by the end of 2024.

As a replacement for third-party cookies, Google introduced 'Topics' which will categorize users into a list of interest-based topics in an anonymized manner. You'll still be able to show users ads, but you won't be able to use granular targeting based on the specifics of what they have engaged with across different websites.