Test for breakage | Privacy Sandbox | Google for Developers
To support testing scenarios during the 1% testing and ramp-up phases of third-party cookie deprecation in Chrome, several Chrome flags are available.
You can also try browsing with third-party cookies blocked using chrome://settings/cookies, but be aware that the flag ensures the new and updated features are also enabled. Blocking third-party cookies is a good approach to detecting issues, but doesn't necessarily help you 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 investigate for third-party cookie dependencies.
In addition to --test-third-party-cookie-phaseout, there are a number of flags available to test different scenarios, such as participation in deprecation trials:
