Utma, utmb, utmz cookies

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Revision as of 12:19, 9 October 2012 by Helpful (Talk | contribs)

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These are primarily notes
It won't be complete in any sense.
It exists to contain fragments of useful information.
The cookies named
come from websites that choose to use Google Analytics. It's primarily used to track visits.

The cookie names likely come from earlier versions, called the Urchin Tracking Module, and are also also by the newer ga.js.

Some details:

  • __utmz stores where a visitor came from (search engine, search keyword, link)
  • __utma stores each user's amount of visits, and the time of the first visit, the previous visit, and the current visit (presumably partly for double checking of this information).
  • __utmb and __utmc are used to check approximately how long you stay on a site: when a visit starts, and approximately ends (c expires quickly). If you look at cookie state changes (e.g. using firecookie), you will see these change regularly.


  • __utmv is used for user-custom variables in Analytics
  • __utmk - digest hashes of utm values (verify)