Does GTM actually slow down your website? (Spoiler: it's complicated)
Original: GTM vs. Page Speed – Impact and How to Improve
May 26, 2025
46 min read
Research
Intermediate
Summary
Data-driven study measuring how GTM containers and tags affect load time.
Who This Is For
Marketing Analysts
Technical Marketers
Performance Marketers
Key Takeaways
- Even asynchronous tags impact website loading speed - empty GTM containers have minimal impact, but the tags you add inside matter most
- Hardcoded tracking tags can actually slow websites down more than the same 8 tags implemented through GTM
- Delaying non-critical tags and firing them later reduces negative performance impact significantly
- Server-side tagging and regular container audits are your best weapons for keeping tracking fast
- DOM manipulations through GTM can add up to 3 seconds to Time to Interactive metrics
Tools & Technologies
Google Tag Manager webpagetest.org Google Lighthouse Server-side Google Tag Manager Various tracking tags and pixels
Topics Covered
tag-management performance google-tag-manager page-speed
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