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title: "A/B Testing Tools Cost 10.2 Points of Good LCP, the Worst of Any Third-Party Category - PageSpeed Matters"
description: "Sites running an A/B testing tool are good on LCP just 58.5% of the time on mobile versus 68.7% without, a 10-point loading penalty and the steepest of any third-party category we measured."
lang: en
json-ld:
---

[A/B Testing Tools Cost 10.2 Points of Good LCP, the Worst of Any Third-Party Category](https://www.pagespeedmatters.com/resources/data-studies/ab-testing-tools-core-web-vitals)

Sites running an A/B testing tool are good on LCP just 58.5% of the time on mobile versus 68.7% without, a 10-point loading penalty and the steepest of any third-party category we measured.

Good loading (LCP) by third-party category, mobile penalty

A/B testing tools

10.2 pts 

Live chat widgets

9.5 pts 

Google Tag Manager

5.3 pts 

Cookie banners

3.7 pts 

Source: PageSpeed Matters analysis of 9.5 million origins with CrUX field data, mobile 75th percentile, mid-2026. Bars scaled to the largest penalty.

A/B testing sits at the top of the list. The anti-flicker snippet is the reason its loading cost outruns every other named tool.

Core Web Vitals pass rate, with and without an A/B tool (mobile)

Without an A/B tool

42.4% 

With an A/B tool

41.5% 

Source: PageSpeed Matters, mobile 75th-percentile field data, mid-2026.

Overall pass barely moves because A/B tools live on stronger sites. The loading damage is real; the site quality masks it.

Source: [A/B Testing Tools Cost 10.2 Points of Good LCP, the Worst of Any Third-Party Category - PageSpeed Matters](https://www.pagespeedmatters.com/resources/data-studies/ab-testing-tools-core-web-vitals)