Unused JavaScript bytes on React sites

Sites with 850 KB to 1.5 MB of unused JS unused JavaScript bytes have a good INP most often: 96%, against 95% of all React sites. Sites with 400 to 850 KB of unused JS unused JS have it least often, at 87%.

Sites with under 400 KB of unused JS unused JavaScript bytes have a good LCP most often: 97%, against 85% of all React sites. Sites with over 1.5 MB of unused JS unused JS have it least often, at 82%.

Over 1.5 MB of unused JS is the most used: 67.5% of React sites. 850 KB to 1.5 MB of unused JS is 25.5% of React sites.

On Wix, 72% of sites use over 1.5 MB of unused JS unused JavaScript bytes, and 97% of Wix sites have a good INP, against 95% of all sites. On WordPress, 64% of sites use over 1.5 MB of unused JS, and 98% of WordPress sites have a good INP.

On Wix, 72% of sites use over 1.5 MB of unused JS unused JavaScript bytes, and 94% of Wix sites have a good LCP, against 85% of all sites. On WordPress, 64% of sites use over 1.5 MB of unused JS, and 61% of WordPress sites have a good LCP.

PlatformUnused JavaScript bytes on its sitesGood INP

All React sites 9,570 sitesOver 1.5 MB unused 68%850 KB to 1.5 MB unused 25%95%

WordPress 2,342 sitesOver 1.5 MB unused 64%850 KB to 1.5 MB unused 22%400 to 850 KB unused 10%98%

Wix 5,824 sitesOver 1.5 MB unused 72%850 KB to 1.5 MB unused 28%97%

Over 1.5 MB unused 850 KB to 1.5 MB unused 400 to 850 KB unused Under 400 KB unused

Does the platform explain the unused JavaScript bytes difference?

On Wix, 97% of sites with 850 KB to 1.5 MB of unused JS unused JavaScript bytes have a good INP, against 97% of Wix sites with over 1.5 MB of unused JS. Within Wix, sites with 850 KB to 1.5 MB of unused JS and over 1.5 MB of unused JS have a good INP about equally often. On WordPress, 99% of sites with 850 KB to 1.5 MB of unused JS unused JavaScript bytes have a good INP, against 98% of WordPress sites with over 1.5 MB of unused JS. Within WordPress, sites with 850 KB to 1.5 MB of unused JS and over 1.5 MB of unused JS have a good INP about equally often.

On Wix, 93% of sites with over 1.5 MB of unused JS unused JavaScript bytes have a good LCP, against 98% of Wix sites with 850 KB to 1.5 MB of unused JS. Within Wix, sites with over 1.5 MB of unused JS have a good LCP less often. On WordPress, 99% of sites with under 400 KB of unused JS unused JavaScript bytes have a good LCP, against 54% of WordPress sites with over 1.5 MB of unused JS. Within WordPress, sites with under 400 KB of unused JS have a good LCP more often.

How dead JavaScript code still blocks the main thread

The browser cannot skip parsing or compiling unused functions inside a downloaded bundle. Across 544 sites (5.7%) with 400 to 850 KB of unused JS, 87% pass field INP at an 84ms median, while the 67.5% (6,461) exceeding 1.5 MB of unused JS drop to 95% good INP (82ms median).