Overview

Google Analytics is a simple, easy-to-use tool that helps website owners measure how users interact with website content. As a user navigates between web pages, Google Analytics provides website owners JavaScript tags (libraries) to record information about the page a user has seen, for example the URL of the page. The Google Analytics JavaScript libraries use HTTP Cookies to "remember" what a user has done on previous pages / interactions with the website.

Google Analytics supports three JavaScript libraries (tags) for measuring website usage: gtag.js, analytics.js, and ga.js. The following sections describe how each use cookies.

Google Analytics

gtag.js and analytics.js set the following cookies:

Cookie Name Expiration Time Description
_ga 2 years Used to distinguish users.
_gid 24 hours Used to distinguish users.
_gat 1 minute Used to throttle request rate. If Google Analytics is deployed via Google Tag Manager, this cookie will be named _dc_gtm_<property-id>.
_gac_<property-id> 90 days Contains campaign related information for the user. If you have linked your Google Analytics and Google Ads accounts, Google Ads website conversion tags will read this cookie unless you opt-out. Learn more.

This library sets the following cookies:

Cookie Name Default Expiration Time Description
__utma 2 years from set/update Used to distinguish users and sessions. The cookie is created when the javascript library executes and no existing __utma cookies exists. The cookie is updated every time data is sent to Google Analytics.
__utmt 10 minutes Used to throttle request rate.
__utmb 30 mins from set/update Used to determine new sessions/visits. The cookie is created when the javascript library executes and no existing __utmb cookies exists. The cookie is updated every time data is sent to Google Analytics.
__utmc End of browser session Not used in ga.js. Set for interoperability with urchin.js. Historically, this cookie operated in conjunction with the __utmb cookie to determine whether the user was in a new session/visit.
__utmz 6 months from set/update Stores the traffic source or campaign that explains how the user reached your site. The cookie is created when the javascript library executes and is updated every time data is sent to Google Analytics.
__utmv 2 years from set/update Used to store visitor-level custom variable data. This cookie is created when a developer uses the _setCustomVar method with a visitor level custom variable. This cookie was also used for the deprecated _setVar method. The cookie is updated every time data is sent to Google Analytics.

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