CLS Checker
Visualise & debug layout shifts (CLS) in the browser
CLS Checker launched on March 22, 2021 with 60 votes, #1,201 of 3,696 launches that month and more than 50% of that year's launches. The site was still online in September 2026, 5 years on.
What it does
This tool measures the 'cumulative layout shifts' that occur when a page is loaded in the browser using data from the Chrome Performance API. These are then listed showing the 'layout shift' score and visualised on the webpage.
Does a similar job
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