What is the _dc_gtm_ cookie?
_dc_gtm_ is a cookie name prefix generated by Google Tag Manager; the full cookie name typically looks like _dc_gtm_UA-XXXXXXXX-Y, where the trailing part is the Google Analytics Universal Analytics (UA) property ID configured in the container.
The cookie appears on a site when the Google Analytics tag inside GTM is configured with cross-domain linking, or with certain tracking settings that require coordination between multiple tag-management scripts on the same page. It is set by the GTM code as the page loads, in the visitor's browser.
What data it stores
The value is typically a simple status flag and does not directly contain personal information such as a name or email address. The exact value format can vary depending on the GTM version and container configuration.
The data stays in the visitor's browser and is read by the Google Tag Manager / Google Analytics scripts loaded on the page; it is not a cookie explicitly transmitted as-is to an external server, but rather helps coordinate tracking scripts internally.
What it is used for
The cookie's purpose is purely technical within the measurement flow: it helps avoid duplicate Google Analytics hits when a page uses multiple tracking methods or cross-domain linking at the same time.
For the site owner, its presence signals that Google Analytics is integrated through Google Tag Manager, used for traffic and visitor-behavior statistics.
Does it require consent?
In CookieFix's classification, _dc_gtm_ falls under the statistics (analytics) category, since it is directly tied to Google Analytics.
- Under GDPR and the ePrivacy Directive (2002/58/EC, transposed in Romania via Law 506/2004), analytics cookies are not strictly necessary for the site to function, so prior visitor consent is required.
- The site owner must disclose this cookie in the cookie policy and ensure the GTM/Analytics script that sets it only fires after consent.
- Periodic site scanning helps automatically detect this type of cookie and keep the disclosed list up to date.
How to block or delete _dc_gtm_
A visitor can delete or block this cookie via the browser's cookie/site-data settings (Chrome, Firefox, Edge, Safari), or use extensions that block tracking scripts / Google Analytics.
At site level, the owner should not let Google Tag Manager fire the Google Analytics tag automatically before consent is given. A consent management platform like CookieFix can automatically block the script from loading until the visitor makes a choice in the banner, preventing the _dc_gtm_ cookie from being set prematurely.
Frequently asked questions
It's a technical cookie set by Google Tag Manager, tied to the site's Google Analytics (UA) property ID, used to coordinate tracking across domains or scripts.
Its typical lifespan is very short, around 1 minute, after which it expires automatically.
Yes, since it is classified as an analytics cookie linked to Google Analytics, it requires the visitor's prior consent under GDPR and Law 506/2004.
Configure the Google Analytics tag trigger in GTM to fire only after consent, or use a CMP that automatically blocks the script until consent is granted.