In order to get your external campaigns tracked within Google Analytics, you need to tag destination URLs. You also need to be aware on some technical pitfalls.

The utm_source paramater is the only parameter really required.

Although Google claims that utm_source, utm_medium and utm_campaign parameters are required, utm_source is the only one really required. If you only set utm_medium and/or utm_campaign, the traffic will be recorded as direct. But if you set at least utm_source, other parameters that are not set will simply have the value “(not set)”.

Never, ever, overwrite campaign parameters during a visit.

The typical case is seen when campaign parameters are used to track internal campaigns. I should not link like this to the post explaining how to tag internal campaigns (unsing these parameters campaign parameters to tag an internal link: utm_source=magnetsearchmarketing.com&utm_medium=textlink&utm_campaign=how-to-not-mess-up-your-google-analytics-campaign-data).

You’re probably wondering what’s so terrible in doing this? I’ve run some tests with source and medium, originally set to s11/m11 and overwritten by s12/m12, s21/m21 by s22/m22, etc. Let’s have a look at the results:

And overall conversions:

How inaccurate are data from overwritten campaigns?

Do you see what happens?

• Conversion rate of 128%, or 9 conversions for 7 visits. Nonsense, since a conversion can only occur once in a visit!
• Sources with 0 visits. Each source/medium combination that have overwritten original source/medium gets 0 visit.
• 0% conversion rate for each item, except the 1st one that had not been overwritten. This means that when a source/medium is overwritten within a session, neither the original or the second element is credited with conversions, although conversions are still recorded at a global level.

These results are completely coherent with these tests on organic keywords, meaning this problem affects any traffic source.

Conclusion

Do not link internal content by using campaign parameters. Use our method to track internal campaigns instead. And if you find some weird data in your campaign reports, think about this issue!

This post was written by Alex