What is the `_gcl_au` Cookie?

Set by Google Ads (Google LLC). Expires after 90 days.

Purpose

Used by Google AdSense to experiment with advertisement efficiency across websites using their services.

Marketing cookies are used to track visitors across websites to display relevant advertisements. Consent is required under GDPR.

Under GDPR and the ePrivacy Directive, the _gcl_au cookie requires explicit user consent before it can be set. This means:

The cookie must not be set when a user first visits your site — not even for a fraction of a second
A consent banner must be displayed, and the user must actively accept analytics/marketing cookies
If the user rejects or ignores the banner, this cookie must remain blocked
The cookie must be listed in your cookie policy with its name, purpose, and retention period
Users must be able to withdraw consent at any time, which must also remove or invalidate this cookie

Block it by default — configure your Consent Management Platform (CMP) or tag manager to prevent Google Ads from loading until the user accepts marketing cookies.
Include it in your consent categories — map it to the "Marketing / Advertising" category in your CMP configuration.
List it in your cookie policy — document the cookie name, purpose, provider (Google LLC), and expiry (90 days).
Sign a DPA — ensure you have a Data Processing Agreement with Google LLC covering their use of data collected via this cookie.
Verify it works — in an incognito browser, reject cookies and confirm _gcl_au is not set.

Cookie	Category	Duration
_gcl_aw	Marketing / Advertising	90 days
_gcl_dc	Marketing / Advertising	90 days

Scan your website to see every cookie it sets, whether they're blocked before consent, and get a full GDPR compliance report.