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High Cumulative Layout Shift (CLS) is a common issue in web design that can negatively impact user experience and SEO rankings. CLS measures how much the content shifts unexpectedly during page load. Addressing the causes of high CLS is essential for creating stable and user-friendly websites.
Understanding the Causes of High CLS
Several factors contribute to high CLS, including images without size attributes, dynamically injected content, and web fonts causing layout shifts. Recognizing these causes helps developers implement targeted solutions.
Images and Media
Images that do not have specified width and height attributes can cause layout shifts as the browser loads them. Always include explicit dimensions or use CSS to reserve space for images and videos.
Web Fonts
Web fonts may cause shifts as they load and replace fallback fonts. To prevent this, use font-display: swap in CSS, ensuring text remains visible during font loading.
Dynamic Content
Content injected after the initial load, such as ads or third-party widgets, can cause unexpected shifts. Reserve space for such content or load it asynchronously to minimize impact.
Strategies to Reduce CLS
Implementing best practices can significantly reduce CLS and improve overall website stability. Here are some effective strategies:
- Specify Size Attributes: Always include width and height attributes on images and videos.
- Reserve Space for Dynamic Content: Use CSS to allocate space for ads and widgets.
- Optimize Web Fonts: Use font-display: swap and preload key fonts.
- Minimize Layout Shifts: Avoid inserting content above existing content unless necessary.
- Use Lazy Loading: Lazy load images and videos to improve load times and stability.
By applying these techniques, developers can create more stable websites that offer a better experience for users and higher SEO rankings.