The State of Web Vitals

Main-thread CPU breakdown on React sites

30.5% of audited sites (2,918) spend over 1,200ms in main-thread scripting during load, pushing median field INP to 56ms (99% good INP) versus 43ms (99% good INP) at 150 to 450ms.

Field data PhoneDesktopAll Scope All sites October 2026 edition · Desktop field outcomes · React sites only
React Scoped to 9,570 sites out of 210,902 analyzed (frameworks) Compare with all sites →

38.6% of React sites use 450 to 1,200ms of scripting CPU main-thread CPU breakdown, and 100% of those sites have a good INP, against 99% of all React sites.

The State of Web Vitals · October 2026 · React: 9,570 crawled sites · 1,979 with desktop field dataBy Arjen Karel · corewebvitals.io/state-of-cwv
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INP pass rate

Sites with 450 to 1,200ms of scripting CPU main-thread CPU breakdown have a good INP most often: 100%, against 99% of all React sites. Sites with over 1,200ms of scripting CPU scripting CPU have it least often, at 99%.

SitesGood, needs improvement, poor INPMedian
All React sites1,97999%48ms
450 to 1,200ms scripting CPU 38.6%647100%45ms
150 to 450ms scripting CPU 26.3%44099%43ms
Over 1,200ms scripting CPU 30.5%79199%56ms
Under 150ms scripting CPU 4.5%10198%53ms
GoodNeeds improvementPoorSites: with Chrome field data
The State of Web Vitals · October 2026 · React: 9,570 crawled sites · 1,979 with desktop field dataBy Arjen Karel · corewebvitals.io/state-of-cwv
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Main-thread CPU breakdown usage

450 to 1,200ms of scripting CPU is the most used: 38.6% of React sites.

450 to 1,200ms scripting CPU 38.6% Over 1,200ms scripting CPU 30.5% 150 to 450ms scripting CPU 26.3%
450 to 1,200ms scripting CPU 38.6% Over 1,200ms scripting CPU 30.5% 150 to 450ms scripting CPU 26.3% Under 150ms scripting CPU 4.5%
The State of Web Vitals · October 2026 · React: 9,570 crawled sites · 1,979 with desktop field dataBy Arjen Karel · corewebvitals.io/state-of-cwv
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Main-thread CPU breakdown per platform

On Wix, 44% of sites use 450 to 1,200ms of scripting CPU main-thread CPU breakdown, and 100% of Wix sites have a good INP, against 99% of all sites. On WordPress, 47% of sites use over 1,200ms of scripting CPU, and 100% of WordPress sites have a good INP.

PlatformMain-thread CPU breakdown on its sitesGood INP
All React sites 9,570 sites450 to 1,200ms scripting CPU 39%Over 1,200ms scripting CPU 30%150 to 450ms scripting CPU 26%99%
Wix 5,824 sites450 to 1,200ms scripting CPU 44%150 to 450ms scripting CPU 31%Over 1,200ms scripting CPU 23%100%
WordPress 2,342 sitesOver 1,200ms scripting CPU 47%450 to 1,200ms scripting CPU 28%150 to 450ms scripting CPU 17%100%
450 to 1,200ms scripting CPU Over 1,200ms scripting CPU 150 to 450ms scripting CPU Under 150ms scripting CPU
The State of Web Vitals · October 2026 · React: 9,570 crawled sites · 1,979 with desktop field dataBy Arjen Karel · corewebvitals.io/state-of-cwv
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Main-thread CPU breakdown or the platform

Does the platform explain the main-thread CPU breakdown difference?

On Wix, 100% of sites with 450 to 1,200ms of scripting CPU main-thread CPU breakdown have a good INP, against 100% of Wix sites with over 1,200ms of scripting CPU. Within Wix, sites with 450 to 1,200ms of scripting CPU and over 1,200ms of scripting CPU have a good INP about equally often. On WordPress, 100% of sites with 450 to 1,200ms of scripting CPU main-thread CPU breakdown have a good INP, against 99% of WordPress sites with over 1,200ms of scripting CPU. Within WordPress, sites with 450 to 1,200ms of scripting CPU and over 1,200ms of scripting CPU have a good INP about equally often.

Why scripting dominates main-thread CPU budgets

Across the web, JavaScript evaluation accounts for the largest share of total main-thread CPU time, dwarfing HTML parsing, style calculation, and painting. Across 2,521 sites (26.3%) spending 150 to 450ms in scripting CPU, 99% pass field INP (43ms median), while the 30.5% (2,918) exceeding 1,200ms drop to 99% good INP (56ms median).

The State of Web Vitals · October 2026 · React: 9,570 crawled sites · 1,979 with desktop field dataBy Arjen Karel · corewebvitals.io/state-of-cwv
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Understanding main-thread CPU breakdown

Audit scripts consuming over 450ms of CPU during boot and yield between hydration, analytics initialization, and DOM manipulation. Across all audited sites, 26.3% spend 150 to 450ms in scripting CPU (99% good INP, 43ms median) versus 30.5% above 1,200ms (99% good INP, 56ms median).

Go fix it Yield to the main thread → Fix excessive DOM size → JavaScript priority levels →
The State of Web Vitals · October 2026 · React: 9,570 crawled sites · 1,979 with desktop field dataBy Arjen Karel · corewebvitals.io/state-of-cwv
Related signals Document lifecycle (lab) → Lab paint timeline → Total Blocking Time (lab) → By Arjen Karel · 9,570 crawled React sites (1,979 with desktop Chrome field data, October 2026) · How we measured