Remove privacy sandbox content from 3rd-party cookies guide

[chrisdavidmills]

Description

With Google's privacy sandbox suite of technologies largely being de-decommissioned (see https://privacysandbox.com/news/update-on-plans-for-privacy-sandbox-technologies/), it makes sense to start removing MDN's coverage of it, and marking impacted features as deprecated.

This PR updates our Third-party cookie guide to remove any mention of the privacy sandbox and impacted features. Note that private state tokens are standardized and are being kept.

Motivation

Additional details

Related issues and pull requests

Fixes #41778

[github-actions]

Preview URLs

• /en-US/docs/Web/Privacy/Guides/Third-party_cookies
• /en-US/docs/Web/Privacy
• /en-US/docs/Web/Security

Flaws (3)

Note! 2 documents with no flaws that don't need to be listed. 🎉

URL: /en-US/docs/Web/Security
Title: Security on the web
Flaw count: 3

• unknown:
  • No generic content config found
  • no blog root
  • no blog root

External URLs (3)

URL: /en-US/docs/Web/Privacy/Guides/Third-party_cookies
Title: Third-party cookies

• https://learn.microsoft.com/en-us/microsoft-edge/web-platform/tracking-prevention (1 time) (Note! This may be a new URL 👀)
• https://webkit.org/tracking-prevention-policy/ (1 time) (Note! This may be a new URL 👀)
• https://webkit.org/tracking-prevention/ (1 time) (Note! This may be a new URL 👀)

(comment last updated: 2025-11-21 15:24:49)

[wbamberg]

Thanks Chris! I had some annoying comments.

[hamishwillee]

Removing myself from review since Will is on this. Add me back if needed.

[chrisdavidmills]

Thanks Chris! I had some annoying comments.

Implies that some of your comments aren't annoying 🤣

Thanks for the review, mate, really useful comments. Answered in the latest commit.

[wbamberg]

👍 thank you Chris! I think in 2026 it would be great to try to have a single comprehensive guide to 3rd party cookies, that integrates this and partitioned cookies and some version of the "firefox tracking protection" page, as well as stuff about what other browsers do.

We're going to be doing some work on the privacy documentation so hopefully it can be a part of that...

[chrisdavidmills]

👍 thank you Chris! I think in 2026 it would be great to try to have a single comprehensive guide to 3rd party cookies, that integrates this and partitioned cookies and some version of the "firefox tracking protection" page, as well as stuff about what other browsers do.

We're going to be doing some work on the privacy documentation so hopefully it can be a part of that...

Yeah, I agree that it would be good to make this more comprehensive. Happy to help if I can.