Third Party Cookies Must Be Removed

Summary

Third-party (AKA cross-site) cookies are harmful to the web, and must be removed from the web platform. This finding explains why they must be removed, and examines the challenges in removing them. We highlight some use cases that depend on third-party cookies and offer some examples of designed-for-purpose technologies that can replace them. Specification authors are expected to ensure they do not undermine the benefits of removing third-party cookies when proposing new web platform technologies. This document is an agreed finding and reflects the consensus of the TAG. ## Introduction We consider privacy a core design principle and differentiator for the web platform (see: [Ethical Web Principles](https://www.w3.org/TR/ethical-web-principles/#privacy), [Unsanctioned Web Tracking](https://www.w3.org/2001/tag/doc/unsanctioned-tracking/), [Private Browsing Modes](https://www.w3.org/2001/tag/doc/private-browsing-modes/), [Privacy Principles](https://www.w3.org/TR/privacy-principles/), [Security & Privacy Questionnaire](https://www.w3.org/TR/security-privacy-questionnaire/)). Many browsers have restricted third-party cookies (see: [Webkit](https://webkit.org/blog/10218/full-third-party-cookie-blocking-and-more/), [Mozilla](https://blog.mozilla.org/en/mozilla/firefox-rolls-out-total-cookie-protection-by-default-to-all-users-worldwide/)). Unfortunately, [not all browsers have followed suit](https://privacysandbox.com/intl/en_us/news/privacy-sandbox-update/). The TAG calls for all browsers to drop support for third-party cookies, as this provides an opportunity to further improve the privacy preserving features of the web platform. Removing third-party cookies from the web platform is not without complications. There are use cases for third-party cookies that need to be preserved, and pitfalls we need to be careful to avoid while doing so. This document sets out some aspects that specification editors and implementors should be aware of in order to make sure we ultimately ...