Cumulative Layout Shift (CLS)

Measures unexpected webpage content shifts.

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    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.

    Guidance

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