Reducing Cumulative Layout Shift on Your Website

Cumulative Layout Shift (CLS) refers to a phenomenon where changes made to an element's position, size, or style on the page cause adjacent elements to reposition themselves as well, leading to an overall visual disruption. The CLS problem arises when developers make changes to the layout of a webpage by adding or removing content, changing font sizes, or altering image dimensions, without properly considering the impact on adjacent elements. This can result in unexpected and often jarring effects, such as text wrapping around images that were previously pushed to the edge of the page. As a consequence, users may experience frustration and difficulty reading the content due to the shifting layout. To mitigate this issue, it is essential to adopt best practices for managing CLS on your website,

What is Cumulative Layout Shift?

Causes of Cumulative Layout Shift

Cumulative Layout Shift (CLS) occurs when a page's content is repositioned or resized after its initial load, resulting in a visual disturbance for the user. This issue often arises from the use of JavaScript code that dynamically updates the layout of web pages, particularly when loading external assets such as images and videos. Additionally, the increasing reliance on lazy loading techniques can lead to CLS if not implemented correctly, as these scripts may be triggered after the initial page load, causing a sudden shift in content positioning. Furthermore, using too many third-party libraries or scripts can increase the risk of CLS, as each script may have its own layout update mechanism that can interfere with other scripts.

Consequences of Cumulative Layout Shift

Cumulative layout shift can have significant consequences for a user's experience and engagement with a website. When images and other content are loaded dynamically, they can cause the layout of the page to shift unexpectedly, leading to a loss of trust and frustration among users. This can result in abandoned carts, missed opportunities, and ultimately, a negative impact on conversion rates. Furthermore, cumulative layout shift can also affect search engine rankings, as Google prioritises websites with stable and consistent layouts. By taking proactive measures to mitigate CLS, website owners can improve the overall user experience and maintain a competitive edge online.

How to Identify Cumulative Layout Shift

1. Ensure that all external stylesheets and scripts are loaded after their referenced content has finished loading to prevent unexpected layout changes.
2. Use the CSS box-sizing property to include padding and border in an element's total width and height, making it easier to predict how elements will resize.
3. Opt for images with fixed-width versions alongside alt-text descriptions, allowing users to easily switch between formats if needed.
4. Implement a technique called 'box-shadow' to create the illusion of movement while loading content without causing layout shift issues.
5. Use relative positioning and float properties judiciously on elements that require dynamic updates or scrolling to maintain visual flow.

Step-by-Step Solution to Reduce CLS

A retail company noticed that their product pages were experiencing significant Cumulative Layout Shift (CLS) issues, resulting in a poor user experience. To address this issue, they implemented the following steps: they wrapped each image and product description in a container element with a fixed width, ensuring consistent spacing between elements. They also adjusted the layout of their content to accommodate different screen sizes and resolutions, using flexible units such as percentages and ems instead of pixels. By making these changes, the company was able to reduce CLS on their website and improve overall user engagement. As a result, they saw an increase in sales and customer satisfaction.