What are large Layout Shifts?

Large layout shifts refer to significant, unexpected movements of webpage content that occur as a page is loading or interacting. These shifts typically happen when visual elements like images, ads, or dynamically loaded content move other elements on the page after the initial view is presented to the user. This can be disorienting and frustrating for users, as it may cause them to click on the wrong button or link accidentally if the layout shifts under their pointer.

These movements are measured by a metric known as Cumulative Layout Shift (CLS), which is part of the Core Web Vitals used by Google to assess the user experience quality of a website. A high CLS score indicates a poor user experience due to excessive shifting of webpage content, which could potentially affect a site’s search engine ranking and user satisfaction. To provide a good user experience, it’s recommended to maintain a low CLS by stabilizing the content as much as possible during the page load.

Avoiding large Layout Shifts

Avoiding large layout shifts in WordPress is crucial for maintaining a smooth and enjoyable user experience. Large layout shifts occur when visible elements on a page move around unexpectedly while the page is loading, which can be frustrating for users trying to interact with your site. Here’s how you can minimize these shifts to boost performance:

Optimize Image and Media Handling

1. Specify Dimensions: Always define width and height attributes for your images and videos. This reserves the necessary space in the webpage layout from the start, preventing shifts when the media loads.
2. Use Aspect Ratio Boxes: For responsive design, use CSS to set aspect ratios that maintain the space while the media loads, preventing jumps.
3. Lazy Loading: Implement lazy loading for images and media files, which means they only load as they enter the viewport (the part of the web page visible to the user). This reduces the risk of shifting elements that have already been displayed.

Stabilize Ad Placement

4. Static Ad Sizes: Reserve the exact size for advertisements on the page. Avoid collapsing ad slots or dynamically resizing them after content has loaded.
5. Avoid Inline Ads in Text: Place ads away from the primary content or in dedicated spaces to prevent reflow.

Control Dynamic Content

6. Avoid Injecting Content Above Existing Content: When dynamically loading content (like with AJAX or APIs), append it below existing content or in designated areas to avoid pushing content down the page.
7. Web Fonts: Flash of Unstyled Text (FOUT) and Flash of Invisible Text (FOIT) can cause layout shifts. Use font-display properties to control how web fonts load and render.

Manage CSS and JavaScript Effectively

8. Optimize CSS Delivery: Use critical CSS (the minimum CSS needed to display the above-the-fold content) inline in the head of your document. This reduces the risk of CSS-related layout shifts.
9. Avoid Large DOM Elements: A complex DOM structure can slow down the page and lead to layout shifts. Simplify your HTML structure and avoid unnecessary nested elements.
10. Minimize JavaScript Execution Time: Delay or defer JavaScript that’s not critical to the initial page load. This minimizes the impact on layout and interactivity.

Use Modern Layout Techniques

11. CSS Grid and Flexbox: These modern CSS layout systems offer more robust ways to design responsive interfaces without unexpected shifts.
12. Sticky Elements: Use CSS for sticky headers or footers rather than JavaScript, as it’s more performance-efficient and less likely to cause layout shifts.

Monitor and Optimize

13. Use Performance Monitoring Tools: Tools like Google’s Lighthouse and Chrome DevTools can help identify and debug layout shifts. Pay attention to the Cumulative Layout Shift (CLS) metric in your performance reports.

By implementing these strategies, you can significantly reduce layout shifts, improve user experience, and boost your site’s performance in WordPress. Regular monitoring and adjustments as part of your web development process are essential to maintain optimal performance as your site evolves.

What is the Cumulative Layout Shift Metric?

Cumulative Layout Shift (CLS) is a performance metric that measures the total sum of all individual layout shift scores for every unexpected layout shift that occurs during the entire lifespan of a page. It’s one of the Core Web Vitals, which are used by Google to evaluate the user experience of a webpage. The metric is crucial because it quantifies how often users experience unexpected content shifts, which can negatively impact usability and user satisfaction.

How to improve CLS

Improving CLS in WordPress involves several strategic steps:

1. Optimize Images and Media:

• Specify Dimensions: Always define width and height attributes for images, videos, iframes, and other media. This practice ensures that the browser can allocate the correct amount of space in the document while the media is loading, preventing layout shifts.
• Use Aspect Ratio Boxes: For responsive images and videos, use CSS aspect ratio boxes to reserve space dynamically based on the width of the screen or container.

2. Avoid Injecting Content Above Existing Content:

• Dynamic Content: Be cautious about where dynamic content (like ads or banners) is inserted. Avoid placing it above existing content or in the middle of a page where it can push down other content as it loads.
• Web Fonts: Avoid the flash of unstyled text (FOUT) or invisible text (FOIT) by properly loading custom fonts. Use the font-display: swap; CSS rule to ensure text remains visible during font loading.

3. Handle Reservations for Ad Elements:

• Static Space for Ads: If your site uses ads, allocate static space for them. Use placeholder containers that match the size of the ads to prevent shifts when they load.

4. Minimize External Embedded Resources:

• Third-party Embeds: Widgets like social media posts, chat functions, or videos can lead to layout shifts. Ensure these are embedded in a way that doesn’t alter the layout unexpectedly as they load.

5. Use CSS for Animations Instead of JavaScript:

• CSS vs. JavaScript: Where possible, use CSS for animations and transitions instead of JavaScript, as CSS is generally more performance-efficient and less likely to cause layout shifts.

6. Optimize and Review Your Theme and Plugins:

• Theme Choice: Choose themes that are optimized for performance, especially those that handle media sizes and responsive layouts well.
• Audit Plugins: Regularly review and audit plugins to ensure they’re not contributing to layout shifts. Disable or replace any plugins that cause significant CLS issues.

7. Monitor and Test Regularly:

• Use Development Tools: Leverage tools like Google’s Lighthouse, WebPageTest, or the Chrome DevTools to monitor your site’s CLS score and identify specific issues.
• Continuous Monitoring: Since website content and structure evolve, regularly check the CLS score, especially after adding new features or content to your site.

By addressing these factors, you can significantly improve the CLS score of your WordPress site, enhancing the user experience and potentially boosting your site’s performance in search engine results.