Behaviour when receiving both UTM and MTM parameters is not documented

[danielhug-cc]

How does Matomo behave when user visits https://www.example.com?mtm_campaign=campy&utm_source=sourcy
(German forum discussion here.)

In the case of mixed MTM and UTM parameters, what is saved in raw data, and what is used for reports?

There are a few variations possible:

1. Overlapping parameters, such as both MTM and UTM campaign or source parameter
2. Mixed, but not overlapping, such as MTM campaign and UTM source, as in above example
3. Some overlapping, some not
4. Does the order play a role?

Documentation might require a new page or fit somewhere here:
https://matomo.org/faq/reports/common-campaign-tracking-use-cases-and-examples/

[MatomoForumNotifications]

This issue has been mentioned on Matomo forums. There might be relevant details there:

https://forum.matomo.org/t/wie-ist-das-wenn-eine-url-utm-und-mtm-enthalt/53855/6

[michalkleiner]

Hi @danielhug-cc, having a quick look it seems the mtm_ params take priority over utm_ params, so if you use both mtm_campaign and utm_campaign with different values the mtm_campaign value will be used. If you mix campaign and source one with mtm and one with utm prefix, that will work fine, the first one for the given property (name, source, keyword, medium etc) is used.
I'll pass it for prioritisation on updating an FAQ or creating a new one on this topic.