Cumulative Layout Shift (CLS)
Measures unexpected webpage content shifts.
Indicators
Impact
(How ScanGov measures tasklist priorities.)
About
Cumulative Layout Shift (CLS) measures how much a webpage's content unexpectedly moves during loading, affecting user experience. A good CLS score is 0.1 or less. Common causes include images or ads without specified dimensions, dynamically added content, and late-loading fonts. To improve CLS, always set size attributes for media, reserve space for ads, and ensure fonts load properly.
Why it's important
Minimizes unexpected page movements, improving user experience by keeping content stable while it loads.User stories
As a user reading the page, I want the content to stay stable while loading so that I don't accidentally click the wrong thing or lose my place.
Error
(ScanGov messaging when a site fails a standard)
Unexpected layout shifts detected.