Cumulative Layout Shift (CLS) is a measure of how much the visual layout of a page shifts as it loads. A high CLS score can lead to a poor user experience, as it can cause unexpected movement of content and buttons, which can result in unintended clicks or frustration. Here are some real-world examples of CLS:
- Mobile News Site: When a user visits a mobile news site, the site may display advertisements that dynamically load as the user scrolls down. However, if the images or videos in these ads shift the layout of the page, it can be a poor user experience. For example, if an image ad suddenly appears above an article the user is reading, it can cause the article to jump down, making the user lose their place. This can be frustrating and can decrease user engagement.
- E-Commerce Website: An e-commerce website may have product images that load as the user scrolls down the page. If the images are not properly sized, they can cause the layout of the page to shift, leading to a poor user experience. For example, if a user is trying to click on a “buy now” button, but the button suddenly moves down as a product image loads, the user may accidentally click on another button or even lose interest in the product altogether.
- Social Media Platform: A social media platform may have a “scroll to top” button that appears when the user scrolls down the page. If this button suddenly appears and shifts the layout of the page, it can be a poor user experience. For example, if a user is trying to read a post and the “scroll to top” button suddenly appears and shifts the content, it can be jarring and lead to the user losing their place.
Overall, it’s important to minimize cumulative layout shift to ensure a positive user experience. This can be achieved through careful design and testing of web pages to ensure that images, videos, and other dynamic content are properly sized and loaded in a way that does not disrupt the layout of the page. By doing so, web developers can create a smooth and enjoyable user experience that keeps users engaged and coming back for more.