Utma, utmb, utmz cookies

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Revision as of 11:21, 1 March 2011 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.

These cookies track visits on sites that use Google Analytics.

The cookies named
are part of Google Analytics, originally by the urchin tracking module, also by the newer ga.js.

Some details:

  • __utmz tracks where a visitor came from (search engine, search keyword, link)
  • __utma tracks each user's amount of visits, and the time of the first, the previous, and the current visit (presumably partly for double checking).
  • __utmb and __utmc are used to track 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)