What is Cumulative Layout Shift?
The Cumulative Layout Shift (CLS) is easy to understand – it refers to the visual stability of a webpage. As one of the core web Vitals, it gauges how much visible content moves unexpectedly during the loading process, impacting the user experience and making it challenging for users to interact with the page.
A high CLS score means more layout shifts. Websites with high CLS scores are very frustrating for users. It can cause them to lose their place on the page or mistakenly click on other elements. Minimising CLS is essential for a better user experience. Moreover, it directly affects search engine rankings.
What Causes Cumulative Layout Shift?
Cumulative Layout Shifts on a website could be due to several reasons. Below is a list of its common causes:
- Images without specified dimensions
- Ads, banners, and embeds
- Dynamically injected content
- Late-loading web fonts
- Unoptimised third-party scripts
- iFrames without size attributes
- Pop-ups and modal windows
- Content reflows due to CSS changes
How To Measure Cumulative Layout Shift?
You can measure CLS with multiple methods. Google Page Speed Insights is the most common tool for measuring it. You can also check it with other tools. Let’s check out all of these in detail.
Google PageSpeed Insights
This tool provides a comprehensive report on your page’s performance. It includes the CLS score as well as other core web vitals and essential features that play a role in web page speed. It identifies the problem and offers suggestions to improve this score as well.
Lighthouse
The second way to measure CLS is by using Lighthouse. Lighthouse built into Chrome DevTools can also help you in checking your CLS
reshepe
You can also use reshepe to check your CLS score as well. Simply sign up and then, analyse the URL. It will provide you with detailed information about CLS and other essential metrics for website speed. Moreover, it will also provide you with personalised suggestions to solve the diagnosed issues as well.
What Is a Good CLS Score?
According to Google, a CLS score of 0.1 or less is considered good. This score means minimal unexpected layout shifts and, eventually, a better user experience. Scores between 0.1 and 0.25 are considered to need improvement. A CLS score above 0.25 is considered poor and can cause critical usability issues. It can also affect your rankings as well.
How To Fix Cumulative Layout Shift?
After identifying issues with Cumulative Layout Shift (CLS), the next step is to fix these issues. Start by thoroughly reviewing the provided insights. Identify the problematic areas like images, ads, or fonts that are raising this score. Then try to fix these problems one by one.
You may be able to solve some of these problems on your while for complicated issues, but you might need a developer. Below are some practical and effective tips to reduce your CLS score
Always Set Image and Video Sizes Upfront
Images and videos without proper dimensions are one of the major causes of high CLS scores. Specify the dimensions for every image and video before uploading. It prevents the browser from resizing elements as they load and maintains a stable layout throughout the page.
Load Important Styles First to Reduce Cumulative Layout Shift (CLS)
The next tip is to prioritize critical CSS to ensure essential styles load first. It helps you avoid layout shifts caused by late-loading styles. This approach helps maintain a consistent appearance as your page loads and reduces unexpected movements.
Choose the Right Font Loading Method
Do you know fonts can also increase your CLS? Use font display strategies like font-display: swap to minimise CLS score. This method allows text to appear immediately with a fallback font. It reduces visible layout changes when the custom font loads.
Preload Essential Content
Preloading key resources such as fonts, images, and scripts can also help you in reducing CLS scores as well. It reduces the chance of layout shifts by making sure essential content is ready as soon as the user interacts with the page.
Avoid Pushing Content Down the Page
Please don’t add new content like banners or pop-ups at the top of the page after it has already loaded. For example, adding a notification bar later can push everything down. It can cause the page to shift and affect the user activity and, as a result, can increase your Cumulative Layout Shift score.
Optimising Third-Party Scripts To Reduce Cumulative Layout Shift
Keep an eye on third-party scripts to make sure they don’t cause content to move around unexpectedly. For example, if you’re using a chat widget that loads slowly, it might push content out of place as well. Load the script in the background or place it where it won’t mess with the rest of your content to avoid this situation. It will help you in keeping your page stable and user-friendly.
Test on Real Devices to Catch Shifts Early
Regular testing on real devices is also essential for avoiding any CLS issues. In this way, you will be able to identify problems that might not be visible in simulated environments. It can also help you in improving the user experience of your website. Hopefully, now you know the answer to your question
Need Assistance To Reduce Cumulative Layout Shift?
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