---
title: "Google Tag Manager Costs 5.3 Points of Good LCP - PageSpeed Matters"
description: "Tag-managed sites are good on LCP about 5 points less often on mobile, yet they pass Core Web Vitals at nearly the same overall rate, because they tend to be better-maintained sites."
lang: en
json-ld:
---

[Google Tag Manager Costs 5.3 Points of Good LCP](https://www.pagespeedmatters.com/resources/data-studies/google-tag-manager-core-web-vitals)

Tag-managed sites are good on LCP about 5 points less often on mobile, yet they pass Core Web Vitals at nearly the same overall rate, because they tend to be better-maintained sites.

Where a tag manager costs you: loading and stability (mobile)

Good LCP with GTM

64.6% 

Good LCP without

69.9% 

Good CLS with GTM

85.3% 

Good CLS without

89.3% 

Source: PageSpeed Matters analysis of 9.5 million origins with CrUX field data, mobile 75th percentile, mid-2026.

The dip shows up in loading (down 5.3 points) and stability (down 4.0 points), exactly where tags injected after render would hurt.

Source: [Google Tag Manager Costs 5.3 Points of Good LCP - PageSpeed Matters](https://www.pagespeedmatters.com/resources/data-studies/google-tag-manager-core-web-vitals)