Cumulative Layout Shift (CLS)
Posted: Tue Apr 22, 2025 6:46 am
Cumulative Layout Shift (CLS) measures the visual stability of a page by detecting unexpected layout changes. These changes often occur when new content is loaded, such as images without precise dimensions or dynamically inserted ads. A high CLS score indicates that a page is unstable , making the experience irritating for users.
Here's how Google defines CLS scores:
Excellent : less than or equal to 0.1 seconds
Improvement needed : less than or equal to 0.25 seconds
Poor : more than 0.25 seconds
A score of 0.1 seconds or less means the page content is completely static rcs data china throughout its lifecycle. A higher score means the content is dynamic.
Typically, layout changes cause:
images,
advertisements,
embeds (or digital vectors),
iframes without dimensions,
dynamic content,
web fonts, causing unstyled text flash or invisible text flash
How to measure Core Web Vitals ?
There are several tools available to measure the status of Core Web Vitals, both using real user data and lab measurements (simulated tests). These tools help website owners track the performance of their Core Web Vitals and identify areas for improvement.
Field tools
Field tools, also known as Real User Monitoring (RUM), reflect the browsing experience of real users . It takes into account real users, different devices, different network connections, and historical data. The result is aggregated for the entire domain or by URL.
Here's how Google defines CLS scores:
Excellent : less than or equal to 0.1 seconds
Improvement needed : less than or equal to 0.25 seconds
Poor : more than 0.25 seconds
A score of 0.1 seconds or less means the page content is completely static rcs data china throughout its lifecycle. A higher score means the content is dynamic.
Typically, layout changes cause:
images,
advertisements,
embeds (or digital vectors),
iframes without dimensions,
dynamic content,
web fonts, causing unstyled text flash or invisible text flash
How to measure Core Web Vitals ?
There are several tools available to measure the status of Core Web Vitals, both using real user data and lab measurements (simulated tests). These tools help website owners track the performance of their Core Web Vitals and identify areas for improvement.
Field tools
Field tools, also known as Real User Monitoring (RUM), reflect the browsing experience of real users . It takes into account real users, different devices, different network connections, and historical data. The result is aggregated for the entire domain or by URL.