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You can also try browsing with third-party cookies blocked via chrome://settings/cookies, but be aware that
the flag ensures the new and updated functionality is also enabled. Blocking third-party cookies is a good
approach to detect issues, but not necessarily validate you have fixed them.

If you maintain an active test suite for your sites, then you should do two side-by-side runs: one with
Chrome on the usual settings and one with the same version of Chrome launched with the --test-third-party-
cookie-phaseout flag. Any test failures in the second run and not in the first are good candidates to investi-
gate for third-party cookie dependencies. Make sure you report the issues you find.

Once you have identified the cookies with issues and understand the use cases for them, you can work
through the following options to pick the necessary solution.

Although Trusted Web Activities and WebAPKs running in Chrome are exempt from the 1% experiment, a
small number of Trusted Web Activity users may be affected. By ensuring that your critical user journeys
are compatible with third-party cookie deprecation, you can be confident they are supported everywhere:
browser, Trusted Web Activity and WebAPK.

3. Use Partitioned cookies with CHIPS

Where your third-party cookie is being used in a 1:1 embedded context with the top-level site, then you may
consider using the Partitioned attribute as part of Cookies Having Independent Partitioned State (CHIPS) to
allow cross-site access with a separate cookie used per site.

To implement CHIPS, you add the Partitioned attribute to your Set-Cookie header:

By setting Partitioned, the site opts in to storing the cookie in a separate cookie jar partitioned by top-level
site. In the example above, the cookie comes from store-finder.site which hosts a map of stores that enables
a user to save their favorite store. By using CHIPS, when brand-a.site embeds store-finder.site, the value of
the fav_store cookie is 123. Then when brand-b.site also embeds store-finder.site they will set and send
their own partitioned instance of the fav_store cookie, for example with value 456.

This means embedded services can still save state, but do not have shared cross-site storage that would al-
low cross-site tracking.