What is the _gcl_gb cookie?
_gcl_gb is an HTTP cookie belonging to the Google Click ID (gcl) cookie family, used by Google Ads for conversion tracking and ad-click attribution. It sits in the same functional group as _gcl_au and _gcl_aw, playing a more specific role in link handling and click-data retention for certain Google flows.
It is set by Google Ads scripts (gtag.js, Google Tag Manager with Google Ads or Floodlight tags) when a visitor arrives via a Google ad or interacts with conversion-related elements. It typically appears on the first page load if the site runs an active Google Ads tag and the user has accepted marketing cookies.
What data it stores
The cookie stores an identifier tied to the ad click (a Google Click ID or a value derived from it), without directly containing a name, email, or other civil identity data. The exact value format may vary and is not publicly documented in detail by Google.
The data is sent to Google's servers (google.com and doubleclick.net domains), where it is used to correlate the ad click with a later on-site action, such as a purchase or form submission.
What it is used for
The main purpose is conversion attribution: Google Ads uses this cookie to determine whether a site visit or action originated from a paid Google campaign. For site owners, this means more accurate reporting on campaign performance and better allocation of advertising budget.
For Google, the cookie helps build a history of ad interactions, later used for automated bid optimization and, indirectly, for personalizing ads shown to the user across other sites in the Google network.
Does it require consent?
_gcl_gb is classified as a marketing/advertising cookie, since it supports ad conversion tracking and user-level attribution. Under the ePrivacy Directive (transposed in Romania via Law 506/2004) and GDPR, this type of cookie must NOT be set before the visitor gives explicit consent.
- Must be listed in the site's cookie policy, under the marketing/advertising category
- The Google Ads script generating it must be blocked until consent is given
- Consent must be granular, revocable at any time, and logged as proof (per ANSPDCP recommendations)
How to block or delete _gcl_gb
A visitor can delete or block this cookie from browser settings (Chrome, Firefox, Edge, Safari), under per-site cookie management, or use ad-tracking blocking extensions. Blocking it does not affect site functionality, only the accuracy of Google's advertising reports.
For site owners, blocking must happen at the technical level, not just declaratively: Google Ads scripts must be paused until the visitor consents to the marketing category. A CMP like CookieFix can automatically block these scripts until consent is obtained, removing the need for manual code changes on the site.
Frequently asked questions
It does not contain direct civil identity data, but it is used for advertising tracking, which is why it is classified as marketing and requires consent.
Its typical duration is around 90 days from being set, after which it expires automatically unless renewed by a new interaction with Google ads.
The site works normally, but Google Ads loses accuracy in attributing conversions to that site's ad campaigns.
Yes, any marketing-category cookie set on the site, including _gcl_gb, must be explicitly listed in the cookie policy with its provider, purpose, and duration.