Cumulative Layout Shift (CLS)

Cumulative Layout Shift (CLS) measures how much the visible content of a webpage shifts during loading. This metric assesses the visual stability of a page, reflecting how much elements move around as the page loads.

What is CLS?

CLS quantifies the total amount of unexpected layout shifts that occur on a webpage. These shifts happen when visible elements like text, images, or buttons move from their initial position during the loading phase. Such movements can disrupt user interaction and degrade the overall experience.

Why CLS Matters for Page Speed

A low CLS score indicates a stable page layout, which enhances user experience by avoiding unexpected changes. High CLS can lead to a frustrating experience for users as they interact with shifting elements, potentially causing clicks on the wrong elements or causing content to appear misaligned.

To improve page speed, it is crucial to reduce CLS. A stable layout helps ensure that users do not experience disruptive shifts, which contributes to a smoother and more responsive page load time.

Impact on SEO

Search engines like Google use user experience signals as ranking factors. A high CLS score suggests poor visual stability, which can negatively impact your SEO performance. Pages with high CLS may experience lower rankings because search engines prioritize user experience. Improving CLS can help enhance SEO by providing a more stable and enjoyable experience for visitors.

How to Improve CLS

To reduce CLS, consider the following practices:

  • Specify Dimensions: Always specify width and height attributes for images and video elements to prevent them from resizing and shifting content.
  • Use Stable Layouts: Avoid inserting content above existing content unless it is necessary. This practice helps prevent unexpected shifts.
  • Optimize Fonts: Use font-display: optional or swap to minimize layout shifts caused by font loading.
  • Manage Ads: Ensure that ads do not cause shifts by reserving space for them or using responsive ad units.

By focusing on these practices, you can improve your page's CLS score, leading to a more stable and engaging user experience and better SEO performance.

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We measure key performance metrics to ensure a good user experience.

Cumulative Layout Shift (CLS)

Measures visual stability. To provide a good user experience, pages should maintain a CLS of less than 0.1.

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