Learn what causes CLS issues in PageSpeed, how to diagnose them using Chrome DevTools, and how to fix them with some simple tips.
Cumulative Layout Shift (CLS) is a metric that measures how much the content on a web page shifts during loading. A high CLS score indicates a poor user experience, as the page elements move unexpectedly and cause frustration. In this article, we will explain what causes CLS issues in PageSpeed, how to diagnose them using Chrome DevTools, and how to fix them with some simple tips.
Table of Contents
What Causes CLS Issues in PageSpeed?
CLS issues in PageSpeed are caused by any element that changes its position or size after the initial rendering of the page. Some common causes of CLS issues are:
- Images and videos without specified dimensions
- Ads, embeds, and iframes without reserved space
- Web fonts causing flashes of unstyled or invisible text
- Dynamically injected content above existing content
These elements can cause the page layout to shift as they load, resize, or reposition, affecting the CLS score. To avoid CLS issues, it is important to reserve enough space for these elements in advance and avoid inserting new content above existing content without user interaction.
How to Diagnose CLS Issues Using Chrome DevTools?
Chrome DevTools is a useful tool to diagnose CLS issues on a web page. To use Chrome DevTools, follow these steps:
- Open the web page you want to analyze in Chrome browser
- Right-click anywhere on the page and select Inspect
- Click on the Performance tab and click on the Record button
- Reload the page and wait for the recording to finish
- Click on the Stop button and look for the Layout Shift events in the summary
- Click on each Layout Shift event to see which elements caused the shift and how much they shifted
- You can also see the CLS score for the page in the Web Vitals section
Using Chrome DevTools, you can identify the elements that cause CLS issues and how to fix them.
How to Fix CLS Issues with Some Simple Tips?
There are some simple tips that can help you fix CLS issues on your web page. Here are some of them:
- Specify the width and height attributes for images and videos in the HTML markup. This helps the browser allocate enough space for them before they load and prevent layout shifts.
- Reserve enough space for ads, embeds, and iframes using CSS. You can use the aspect-ratio property or the padding-top trick to create responsive containers for them and avoid layout shifts.
- Optimize font delivery using preload, font-display, or subsetting. This helps the browser load the fonts faster and prevent flashes of unstyled or invisible text that can cause layout shifts.
- Avoid inserting new content above existing content without user interaction. This can cause the content to move unexpectedly and affect the user experience. If you have to insert new content, such as banners or pop-ups, make sure to reserve enough space for them or use user gestures to trigger them.
By following these tips, you can improve your CLS score and provide a better user experience for your visitors.
Frequently Asked Questions (FAQs)
Question: What is a good CLS score?
Answer: According to Google, a good CLS score is 0.1 or less. A CLS score between 0.1 and 0.25 needs improvement, and a CLS score above 0.25 is poor.
Question: How does CLS affect SEO?
Answer: CLS is one of the Core Web Vitals, which are a set of metrics that measure the user experience of a web page. Google uses the Core Web Vitals as a ranking factor for search results, especially for mobile devices. Therefore, having a good CLS score can help you rank higher on Google and attract more organic traffic.
Question: How can I measure CLS for my web page?
Answer: You can measure CLS for your web page using various tools, such as:
- PageSpeed Insights: A tool that analyzes the performance and user experience of a web page and provides suggestions to improve them.
- Lighthouse: A tool that audits the quality and accessibility of a web page and generates a report with scores and recommendations.
- Chrome DevTools: A tool that helps you debug and optimize your web page using various features, such as performance analysis, layout inspection, and network monitoring.
- Web Vitals Library: A JavaScript library that helps you measure and report the Core Web Vitals for your web page using real user data.
Summary
CLS is a metric that measures how much the content on a web page shifts during loading. A high CLS score indicates a poor user experience, as the page elements move unexpectedly and cause frustration. To diagnose CLS issues, you can use Chrome DevTools to identify the elements that cause layout shifts and how much they shift. To fix CLS issues, you can follow some simple tips, such as specifying dimensions for images and videos, reserving space for ads and embeds, optimizing font delivery, and avoiding inserting new content above existing content without user interaction. By improving your CLS score, you can provide a better user experience for your visitors and improve your SEO ranking.
Disclaimer: This article is for informational purposes only and does not constitute professional advice. We are not responsible for any damages or losses caused by following the suggestions in this article. Always consult with a qualified web developer before making any changes to your web page.