Google Tag Manager is the more common of the two in our index: it runs on 27,441 websites against 290 for Matomo Tag Manager, and 117 sites use both. Counts come from real scans, not vendor claims.
Google Tag Manager is a tag management system (TMS) that allows you to quickly and easily update measurement codes and related code fragments collectively known as tags on your website or mobile app.
Matomo Tag Manager manages tracking and marketing tags.
117 sites run both Google Tag Manager and Matomo Tag Manager. That is 40% of the sites using Matomo Tag Manager, the smaller of the two.
Want to know which one a particular site uses? Look it up and see its whole stack, or compare two sites side by side.