The Private Advertising Technology Working Group has published a First Public Working Draft of Privacy-Preserving Attribution: Level 1. This specifies a browser API for the measurement of advertising performance. The goal is to produce aggregate statistics about how advertising leads to conversions, without creating a risk to the privacy of individual web users.
Read more at:
https://www.w3.org/news/2025/first-public-working-draft-privacy-preserving-attribution-level-1/