Safari 27.2 fixes a specific CNAME-related cookie lifetime issue

What changed

This is a specific networking correction, not the removal of all Safari tracking limits or a universal recovery of conversion windows. Re-test the affected setup on updated browsers and keep separate identity-domain blocking issues distinct.

A cookie lifetime can be affected by the context in which it is set, the browser's protections and the site's own configuration. The Safari 27.2 note concerns a particular combination: a top-level navigation response and a hostname that resolves through a CNAME to a different registrable domain. It should not be generalised to every first-party cookie or every server-side measurement setup.

For a site that appears to match the described case, compare behaviour on the relevant browser versions using the same navigation and cookie-setting conditions. Record the cookie attributes and observed expiry instead of relying only on the intended lifetime in application code. A controlled reproduction is more informative than an aggregate conversion-window comparison across mixed browser versions.

Keep this networking correction distinct from separate Safari restrictions on identity-related domains. Removing an unintended cap in one context does not mean the browser has stopped applying its other privacy protections. It also does not establish that historical conversions will be recovered or that every visitor can now be recognised for a longer period.

The measurement implication is to revisit the specific affected setup, document the result and update internal assumptions only where the test supports it. Avoid changing consent behaviour or collecting additional identifiers merely to reproduce an expected advertising outcome.

Jen Simmons is the signed announcement author and Ronan Shields is retained as reporting credit. The article uses the 26 October release-note date. Its scope is the documented fix, not a broader claim that Safari has reversed its tracking policy.