mtm_campaign

What the mtm_ tags record

Matomo's campaign plugin documents eight of them: mtm_campaign (the campaign name, its examples are mailing_2017_03 and Easter_Sale), mtm_source (such as google or facebook), mtm_medium (such as email or cpc), mtm_keyword, mtm_content, mtm_cid (a campaign ID code), mtm_group and mtm_placement.

The values are labels the sender chose. They say which mailing or ad a click came from, and everyone who clicks the same link carries the same label.

Why there are four prefixes

Matomo was called Piwik until version 3.3.0, whose changelog opens with the line "Piwik is now Matomo" and links the January 2018 announcement. The older tags kept the old name: pk_campaign and piwik_campaign mean what mtm_campaign means, and pk_kwd and piwik_kwd what mtm_kwd means.

Matomo still reads all of them. Its default configuration lists pk_cpn, pk_campaign, piwik_campaign, mtm_campaign and matomo_campaign as campaign-name parameters, and it reads Google's utm_campaign, utm_source and utm_medium too.

Does removing them break the link?

No. Matomo reads the tags when the page loads in order to file the visit under a campaign; the page itself does not depend on them. Matomo's campaign plugin also leaves these tags out of the page addresses it records.

How LinkClean removes them

Default-on and global: 23 names, the eleven mtm_ fields plus the pk_, piwik_ and matomo_ spellings. A few rarer spellings that Matomo also accepts, pk_cpn and matomo_kwd among them, are not in the list yet. AdGuard's filter and Brave strip the main mtm_ names too, and ClearURLs removes every name that starts with mtm.