CLS shift concentration on React sites

Sites with a single dominant shift CLS shift concentration have a good CLS most often: 74%, against 80% of all React sites. Sites with mostly one shift shift concentration have it least often, at 64%.

A single dominant shift is the most used: 59.3% of React sites.

Wix sets the CLS shift concentration to a single dominant shift on 73% of its sites, and 96% of Wix sites have a good CLS, against 80% of all sites.

PlatformCLS shift concentration on its sitesGood CLS

React sites with CLS shift concentration 3,993 sitesSingle dominant shift (95%+) 59%Mostly one shift (65-94%) 22%Multiple compounding shifts (<65%) 18%80%

Wix 1,197 sitesSingle dominant shift (95%+) 73%Multiple compounding shifts (<65%) 14%Mostly one shift (65-94%) 13%96%

WordPress 1,723 sitesSingle dominant shift (95%+) 55%Mostly one shift (65-94%) 25%Multiple compounding shifts (<65%) 19%75%

Single dominant shift (95%+) Mostly one shift (65-94%) Multiple compounding shifts (<65%)

Does the platform explain the CLS shift concentration difference?

On WordPress, 75% of sites with a single dominant shift CLS shift concentration have a good CLS, against 66% of WordPress sites with mostly one shift. Within WordPress, sites with a single dominant shift and mostly one shift have a good CLS about equally often.

One isolated layout jump versus cascading multi-element shifts

CLS concentration measures the ratio of the single largest layout shift to total lab CLS on pages with non-zero shift. Across 2,367 sites (59.3%) where one isolated element accounts for at least 95% of total CLS, 74% pass field CLS. When secondary shifts join in (22.4% at 65% to 94% concentration), good field CLS drops to 64%, and when shifts are spread across multiple compounding events (18.3%, 730 sites), good field CLS falls to 67%.