Glossary term
What is CLS (Cumulative Layout Shift)?
CLS stands for Cumulative Layout Shift.
In The Browser Contract
A score for how much the page content jumps around by surprise. Good is 0.1 or less.
Learn it properly · The Browser ContractLesson 9: Core Web Vitals for Engineers: LCP, INP and CLSWhat each metric measures, its “good” limit at the 75th percentile, why INP replaced FID, and the difference between field data and lab data.In Scenario Debugging
A score for how much visible content jumps by surprise while the page loads. Fix it by reserving space.
Learn it properly · Scenario DebuggingLesson 8: Layout Shift and Janky InteractionsLayout shift from images, ads and late fonts, and slow input from heavy event handlers. It ends with a short checklist.