When Does a Google Analytics Session Expire, Really?

One of the many ways that Google Analytics and Adobe Analytics differ are their individual definitions of what constitutes a session. Both abide by the industry standard of a session ending after 30 minutes of inactivity*.

* Unless you’ve changed the session timeout setting in a Google Analytics property, or the visit definition/visit timeout setting in an Adobe Analytics virtual report suite.

But Google Analytics has an additional trigger for ending a session that can be a real gotcha when trying to matchback data across the two tools: it ends a session and starts a new one “every time a user’s campaign source changes.” That statement always perplexes me because I’m not sure whether to interpret that as:

  1. when any UTM parameter changes, or…
  2. when only the utm_campaign parameter changes

I always assumed #1, but I decided to test this out so I’d be 100% sure. In each test scenario below, I opened a new guest browser window so none of my activity from each test would overlap.

Test 1: Changing only utm_medium

I loaded two URLs with identical values for utm_source, utm_campaign, and utm_id, but different values for utm_medium.

  • kotaraindustries.com?utm_medium=affiliate&utm_source=halee.com&utm_campaign=201810101234&utm_id=201810101234
  • kotaraindustries.com?utm_medium=partner&utm_source=halee.com&utm_campaign=201810101234&utm_id=201810101234

When I pull up the report by one of the other parameters, it shows two sessions, validating that a new session was started when I loaded that second page.

Test 2: Changing only utm_source

In a new, fresh guest window, I loaded two URLs with identical values for utm_medium, utm_campaign, and utm_id, but different values for utm_source.

  • kotaraindustries.com?utm_medium=affiliate&utm_source=benicetobears.com&utm_campaign=201810101232&utm_id=201810101232
  • kotaraindustries.com?utm_medium=affiliate&utm_source=benicetootters.com&utm_campaign=201810101232&utm_id=201810101232

Again, two sessions:

Test 3: Changing only utm_campaign

In a newer, fresher guest window, I loaded two URLs with identical values for utm_medium, utm_source, and utm_id, but different values for utm_campaign.

  • kotaraindustries.com?utm_medium=affiliate&utm_source=nxt.com&utm_campaign=201810101230&utm_id=201810101230
  • kotaraindustries.com?utm_medium=affiliate&utm_source=nxt.com&utm_campaign=201810101231&utm_id=201810101230

How many sessions? Two sessions!


Test 4: Changing only utm_id

In the newest, freshest of guest windows, I loaded two URLs with identical values for utm_medium, utm_source, and utm_campaign, but different values for the elusive and not-often-used utm_id.

  • kotaraindustries.com?utm_medium=affiliate&utm_source=wwe.com&utm_campaign=201810101228&utm_id=201810101228
  • kotaraindustries.com?utm_medium=affiliate&utm_source=wwe.com&utm_campaign=201810101228&utm_id=201810101229

I think I can stop and not bother with utm_keyword and utm_content, right?


So there you go. Irrefutable evidence that a new session starts on change of any UTM parameter.