Cumulative Layout Shift (CLS) is a web performance metric that measures how much a page’s layout shifts as it loads. In this blog post, we’ll explore what CLS is and how it affects your website’s page speed.
What is Cumulative Layout Shift (CLS)?
CLS measures the amount of unexpected layout shift that occurs during the loading of a web page. This means that it measures the movement of page elements that were not expected to move during the loading process. The metric is expressed as a score between 0 and 1, where a lower score indicates less shifting, and a higher score indicates more shifting.
Why is CLS Important?
CLS is important because it directly impacts the user experience on your website. When page elements shift unexpectedly, users can become disoriented and confused. This can lead to a lower engagement, higher bounce rates, and even lost revenue. Additionally, CLS is one of the Core Web Vitals, a set of metrics used by Google to evaluate website speed and user experience. Websites with a high CLS score may be penalized in search engine rankings.
How to Measure CLS?
CLS can be measured using various tools, including Google’s Lighthouse, PageSpeed Insights, and WebPageTest. These tools can provide valuable insights into your website’s performance and provide recommendations on how to optimize your website’s CLS.
How to Optimize CLS?
Several factors can affect CLS, including images and videos without dimensions, dynamically injected content, and slow-loading fonts. To optimize CLS, you can take the following steps:
- Size Images and Videos Correctly
Images and videos without dimensions can cause layout shifts during the loading process. To optimize CLS, you can specify the dimensions of images and videos in the HTML code.
- Avoid Dynamically Injected Content
Dynamically injected content, such as ads or social media widgets, can cause layout shifts during the loading process. To optimize CLS, you can avoid dynamically injected content or use placeholders to reserve space for them before they load.
- Optimize Web Fonts
Slow-loading web fonts can cause layout shifts during the loading process. To optimize CLS, you can use web fonts that load quickly or use font-display to display fallback fonts until the web font loads.
Cumulative Layout Shift (CLS) is a critical metric that measures the amount of unexpected layout shift that occurs during the loading of a web page. A high CLS score can negatively impact the user experience, search engine rankings, and ultimately, your online success. To optimize CLS, you can size images and videos correctly, avoid dynamically injected content, and optimize web fonts. By optimizing CLS, you can improve your website’s page speed, user experience, and overall success. We recommend that you regularly monitor and optimize your website’s CLS to provide your users with an excellent experience and stay ahead of the competition.