Google Tag Manager is the more common of the two in our index: it runs on 27,416 websites against 353 for Tealium, and 167 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.
Tealium provides a sales enterprise tag management system and marketing software.
167 sites run both Google Tag Manager and Tealium. That is 47% of the sites using Tealium, 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.