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.
Important: Google Analytics does not collect any personal information about your website users. Read the Google Analytics privacy document for more details.
Google Analytics supports two JavaScript libraries (tags) for measuring website usage: analytics.js and ga.js. The following sections describe how each use cookies.
analytics.js – Cookie Usage
The analytics.js JavaScript library is party of Universal Analytics and uses a single first-party cookie containing an anonymous identifier used to distinguish users.
By default, this library sets cookies on the top level domain, excluding the leading dot, and sets the cookie path to the root level (/).
Note: The analytics.js library does not require setting cookies to transmit data to Google Analytics.
This library sets the following cookies:
| Cookie Name | Expiration Time | Description |
|---|---|---|
_ga |
2 years | Used to distinguish users. |
Customization
Read the analytics.js Domains & Cookies developer guide to learn all the ways these default settings can be customized.
Read the Security and privacy in Universal Analytics document for more information about Universal Analytics and cookies.
ga.js – Cookie Usage
The ga.js JavaScript library uses first-party cookies to:
- Determine which domain to measure
- Distinguish unique users
- Remember the number and time of previous visits
- Remember traffic source information
- Determine the start and end of a session
- Remember the value of visitor-level custom variables
By default, this library sets cookies on the domain specified in the document.host browser property and sets the cookie path to the root level (/).
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. |
__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. |
