What is the _gac_ cookie?
_gac_ is a tracking cookie used by Google Ads together with Google Analytics when a website runs Google Ads campaigns and has Google Ads–Google Analytics account linking enabled. The cookie name has a prefix (_gac_) followed by an identifier of the linked Google Analytics property.
It appears in the browser as soon as a visitor lands on the site via a click from a Google Ads advertisement, provided the site has the Google Ads or Google Analytics tag installed with linking active. It does not appear for visitors coming from organic search or other sources.
What data it stores
_gac_ stores information related to the Google Ads campaign that generated the visit — typically parameters such as gclid (Google Click Identifier) along with campaign, ad group, and click-timing data. The exact value format isn't publicly documented in detail by Google and may vary.
This data is sent to Google Ads and Google Analytics servers, where it is used to connect the initial ad click to the user's subsequent actions on the site (e.g., form submission, purchase).
What it is used for
The main purpose is conversion attribution: Google Ads uses this cookie to determine whether a click on an ad later led to a valuable action on the site (a purchase, sign-up, or call). For the site owner, this data feeds conversion reports in Google Ads and supports optimizing paid advertising campaigns.
Without this cookie, measuring the effectiveness of Google Ads campaigns becomes significantly less accurate, especially when combined with Google Analytics integrations.
Does it require consent?
_gac_ is classified as a marketing cookie (advertising and tracking) and is not strictly necessary for the website to function. Under GDPR and the ePrivacy Directive (transposed in Romania via Law 506/2004), this type of cookie requires the visitor's prior, explicit consent, obtained through a compliant cookie banner.
The site owner should: declare this cookie in the cookie policy, classify it under the marketing category in the consent banner, and ensure the Google Ads/Analytics script that sets it does not fire before consent is given.
How to block or delete _gac_
A visitor can delete or block _gac_ through browser settings (Chrome, Firefox, Edge, Safari) under per-site cookie management, or by using ad-blocking/tracking-prevention extensions.
- At the site level, the cookie should be blocked automatically until consent is given, using a CMP that prevents Google Ads/Analytics scripts from running before acceptance — for example, CookieFix automatically blocks such marketing scripts until the visitor gives consent.
- Site owners should correctly configure triggers in Google Tag Manager (if used) so that Google Ads conversion tags only fire after consent is granted.
Frequently asked questions
It's a cookie set by Google Ads (together with Google Analytics) to track ad clicks and measure subsequent conversions on a website.
It typically expires after 90 days, though the exact duration can vary depending on the specific Google Ads/Analytics account setup.
No, it's a marketing/tracking cookie and requires the visitor's prior consent under GDPR and ePrivacy rules.
By using a CMP that prevents Google Ads and Google Analytics scripts from executing before the visitor accepts the marketing category, such as the automatic blocking provided by CookieFix.