If you’ve ever looked at your browser cookies and wondered what all those __utm entries are, they come from Google Analytics. Each one tracks different aspects of visitor behavior on your site.

__utma, __utmb, __utmc and __utmz are 4 cookies created by Google Analytics, for a detailed and very informative read, go here and here.

There’s a longer note on programming over here.

In short: __utma identifies unique visitors, __utmb and __utmc track session activity, and __utmz stores the traffic source info like which campaign or search term brought the user in. These cookies are from the older Universal Analytics — if you’ve migrated to GA4, it uses a different cookie scheme entirely.