Utma, utmb, utmz cookies

The cookies named 

__utma

 through 

__utmz

 are stored by websites that choose to use Google Analytics to see how people visit their websites.

The cookie names seem to come from an earlier versions called the Urchin Tracking Module. These cookie names are still used by the newer ga.js.
Some details:
  • __utmz records whether the visitor came from a search engine (and if so, the search keyword used), a link, or from no previous page (e.g. a bookmark).
  • __utma stores the amount of visits (for each visitor), the time of the first visit, the previous visit, and the current visit
  • __utmb and __utmc are used to check approximately how fast people leave: 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.
Also:
  • __utmv is used for user-custom variables in Analytics
  • __utmk – digest hashes of utm values (verify)
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