What is the __utmb cookie?
__utmb belongs to the cookie family of the classic Google Analytics version (based on the urchin.js library, later ga.js), still used by older sites or ones only partially migrated to Google Analytics 4. It is set by Google's analytics script directly from the visitor's browser, on the first page load where the tracking code runs.
The cookie appears as soon as a visitor opens a page containing the Google Analytics Classic tag, regardless of whether it was properly declared in the site's cookie policy.
What data it stores
__utmb stores a numeric identifier used internally by Google Analytics to calculate the duration of the current session and determine when a session ends (after 30 minutes of inactivity). The exact value format is not documented in detail by Google and may vary.
Data collected through this cookie is sent to Google's analytics servers, where it is used to link successive requests from the same visitor within a single browsing session.
What it is used for
The main purpose of __utmb is session demarcation: Google Analytics uses this cookie to decide whether a pageview belongs to the current session or starts a new one. It underpins classic reports such as "sessions," "pages per session," and "average session duration."
For site owners, this data helps understand visitor behavior — how many distinct sessions the traffic generates, how long users stay, and how often they return within the same visit.
Does it require consent?
__utmb is classified as a statistics (analytics) cookie and is not strictly necessary for the website to function. Under the GDPR and the ePrivacy Directive (implemented in Romania via Law 506/2004), setting this cookie requires the visitor's prior, explicit consent, given through an active action in the consent banner.
Site owners must list this cookie in their cookie policy, correctly categorize it under "statistics," and ensure the Google Analytics Classic script does not run before consent is obtained.
How to block or delete __utmb
Visitors can delete or block __utmb through their browser's privacy settings (Chrome, Firefox, Edge, Safari), either by clearing existing cookies or blocking cookies from Google Analytics domains. The official "Google Analytics Opt-out Browser Add-on" also prevents data collection.
- From the browser: delete cookies for the site's domain or block third-party/tracking cookies.
- From the site's side: use a CMP such as CookieFix, which automatically blocks the Google Analytics Classic script until the visitor consents to the "statistics" category.
Frequently asked questions
Yes. As an analytics cookie, __utmb may only be set after the visitor has given explicit consent in the cookie banner, in line with the GDPR and Romania's Law 506/2004.
It typically lasts 30 minutes of inactivity; each new interaction from the visitor refreshes this window, extending the current session.
No. __utmb belongs to classic Google Analytics (Universal Analytics/urchin.js); GA4 uses a different cookie set, such as _ga and _ga_<container-id>.
The site risks non-compliance with data protection law and potential sanctions from the supervisory authority, since the cookie collects behavioral data without proper disclosure or consent.