3rd-party cookies

Chrome abandoned its 3rd-party cookie phase-out in 2025 in favour of user choice; Safari and Firefox have long blocked them, tracking built on this stays structurally unreliable.

What we check

Inventories cross-domain sources (script, pixel, iframe) that set third-party cookies.

Why it matters

Chrome abandoned its 3rd-party cookie phase-out in 2025 in favour of user choice; Safari and Firefox have long blocked them, tracking built on this stays structurally unreliable.

Common causes

Old retargeting and ad pixels from past campaigns keep setting cross-domain cookies.
Embedded iframes (YouTube, Maps, social widgets) simply bring their third-party cookies along.
Affiliate and attribution services still work on a third-party basis instead of a first-party subdomain.
A forgotten chat or personalisation widget loads tracking from third-party domains.

The fix

Migrate to server-side tagging and switch attribution to CAPI / Enhanced Conversions.

Matching template

CMP and GTM Consent QA Template

The repeatable test plan for default-denied, consent update and reject, across all four signals.

Get the QA template →

Check it yourself first

The Tracking Check tests this point along with all the others, in seconds.

Start the Tracking Check →

Asked often

What does a failing "3rd-party cookies" check mean?

Chrome abandoned its 3rd-party cookie phase-out in 2025 in favour of user choice; Safari and Firefox have long blocked them, tracking built on this stays structurally unreliable. Migrate to server-side tagging and switch attribution to CAPI / Enhanced Conversions.

How do you fix a failing "3rd-party cookies" check?

Migrate to server-side tagging and switch attribution to CAPI / Enhanced Conversions.

The fix, delivered

Wired up in days, not sprints.

Findings from the Tracking Check go into a ranked sequence with effort estimates in the Audit Sprint, every module with an acceptance criterion.

To the service Request an Audit Sprint