Cookie database › Google Tag Manager

gtm_session_start cookie

Analytics cookie set by Google Tag Manager.

Is gtm_session_start firing on your site before anyone says yes?

Conzent holds gtm_session_start and every other analytics cookie until the visitor accepts, and Consent Mode v2 keeps your Google Ads and GA4 reporting accurate. Registered IAB TCF CMP, Google-certified. From €7 per site a month.

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What the gtm_session_start cookie does

Measures how long an activity takes and collects information about user website usage.

Who sets it

Consent category: analytics

Analytics cookies measure how a site is used, in aggregate: pages seen, sessions, where visitors came from. Under the GDPR they need consent before they are set, and Google Consent Mode can model what is lost when visitors decline.

Namegtm_session_start
CategoryAnalytics
Set byGoogle Tag Manager

Other cookies from the same vendor

Is this cookie on your site?

Conzent's scanner lists every cookie your site sets, classifies each one the way this page does, and shows which are set before the visitor has consented. Try Conzent free for 14 days, or look up another cookie.

From the Conzent cookie database, last updated 2026-10-12. Descriptions come from vendor documentation, cookie policies and our own scans; write to support@getconzent.com to correct one.