WordPress CLS shift concentration and the Core Web Vitals

Sites with a single dominant shift CLS shift concentration have a good CLS most often: 91%, against 90% of all WordPress sites. Sites with multiple compounding shifts shift concentration have it least often, at 84%.

A single dominant shift is the most used: 57.7% of WordPress sites.

jQuery sets the CLS shift concentration to a single dominant shift on 57% of its sites, and 90% of jQuery sites have a good CLS, against 90% of all sites.

FrameworkCLS shift concentration on its sitesGood CLS

WordPress sites with CLS shift concentration 44,905 sitesSingle dominant shift (95%+) 58%Mostly one shift (65-94%) 24%Multiple compounding shifts (<65%) 18%90%

jQuery 43,137 sitesSingle dominant shift (95%+) 57%Mostly one shift (65-94%) 24%Multiple compounding shifts (<65%) 19%90%

Vue 3,629 sitesSingle dominant shift (95%+) 57%Mostly one shift (65-94%) 25%Multiple compounding shifts (<65%) 18%90%

React 1,655 sitesSingle dominant shift (95%+) 55%Mostly one shift (65-94%) 25%Multiple compounding shifts (<65%) 19%88%

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

Does the framework explain the CLS shift concentration difference?

On jQuery, 91% of sites with a single dominant shift CLS shift concentration have a good CLS, against 87% of jQuery sites with mostly one shift. Within jQuery, sites with a single dominant shift have a good CLS more often. On Vue, 90% of sites with a single dominant shift CLS shift concentration have a good CLS, against 87% of Vue sites with mostly one shift. Within Vue, 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 25,913 sites (57.7%) where one isolated element accounts for at least 95% of total CLS, 91% pass field CLS. When secondary shifts join in (24.1% at 65% to 94% concentration), good field CLS drops to 87%, and when shifts are spread across multiple compounding events (18.2%, 8,189 sites), good field CLS falls to 84%.