By Shad Super in Questions —

How Do Cumulative Layout Shifts (CLS) Affect a Website's User Experience, and What Strategies Can Webmasters Employ to Minimize Them?

Summary

Cumulative Layout Shift (CLS) is a metric that measures visual stability by quantifying how much unexpected layout shifts impact the user experience on a webpage. Minimizing CLS involves optimizing image and ad sizes, using reserved spaces for dynamic content, and employing appropriate CSS practices. This guide outlines strategies for webmasters to reduce CLS and improve user experience.

Understanding Cumulative Layout Shift (CLS)

CLS is one of Google's Core Web Vitals, emphasizing the importance of visual stability. A low CLS score indicates that a site is correctly stabilizing content such as images, ads, and fonts, reducing unexpected movements that can frustrate users [Cumulative Layout Shift (CLS), 2023].

Impact of CLS on User Experience

High CLS scores can have several negative effects on user experience:

  • Frustration: Users may accidentally click on the wrong content due to unexpected shifts, leading to frustration.
  • Accessibility: Layout shifts can particularly affect users with visual or motor impairments who rely on predictable interface behavior.
  • Trust: A website that shifts unexpectedly might be perceived as unprofessional or unreliable.

Strategies to Minimize CLS

Image Size Optimization

Define explicit width and height attributes or aspect ratios for images to reserve space before the images load. This prevents images from shifting the layout once they are rendered [Optimize CLS, 2023].

Ad Space Reservation

Allocate sufficient space for ads within the layout. Use CSS to create containers with fixed dimensions or aspect ratios to ensure ads don't cause layout shifts when they load asynchronously [Optimize Images, 2022].

Dynamic Content Placeholder

For dynamic content such as embedded widgets or videos, use placeholders of the same size to mitigate layout shifts when the content loads. This can involve using skeleton screens or loading animations [Preventing Content Shifts, 2023].

Font Loading Optimization

Implement font-display options such as <font-display: swap> to ensure text remains visible while custom fonts load. This reduces the risk of layout shifts caused by late font rendering [Font Display, 2022].

Minimal Use of Transform Animations

Avoid animations that change the layout, such as those using transform properties. If animations are necessary, ensure they do not affect the layout or use properties that do not trigger reflows [Animation Performance, 2023].

Conclusion

Reducing CLS is crucial for providing a smooth and stable user experience. By reserving space for images and ads, optimizing font loading, and using effective CSS practices, webmasters can significantly lower CLS scores and enhance the overall performance of their websites.

References