GA Campaign Tracking Parameters: What's Really Required?

Google Analytics campaign tracking is great, and we’ve talked about it lots before. The official story with the campaign tracking parameters is that Campaign, Source, and Medium (utm_campaign, utm_source, utm_medium) are all required. It says so in the the URL builder tool, for example.

I wondered though, what would happen if you left one or two of these off? Would campaign tracking still work?

The short answer is: As long as you include a source (utm_source), campaign parameters still work.

If the URL has the utm_source parameter, cookies get set correctly. If it has one of the other parameters but no utm_source, the cookies about where a visitor came from don’t get re-set at all (similar to using utm_nooverride=1).

What does it look like in reports? If you leave off either utm_medium or utm_campaign, you just get “(not set)” as the value for those fields (shown here in the All Traffic Sources and Campaign reports):

Although I still recommend using all three fields for campaign tracking, this does have one take-home lesson: If you have situations in which URLs might get cut off (such as a plain-text email), always put the source first. This will help ensure you’ll at least get some data even if the other parameters are lopped off.