Cumulative Layout Shift (CLS) in Digital Marketing: Why a Stable Website Matters
What is Cumulative Layout Shift (CLS)?
Cumulative Layout Shift (CLS) is a Core Web Vital that measures the visual stability of a webpage. It quantifies how much elements shift around unexpectedly as the page loads. Imagine you’re about to click a button, and suddenly the page jumps, making you click something else – that’s a bad CLS!
Why is CLS Important?
CLS is crucial for a positive user experience (UX):
- Frustration: Unexpected shifts are annoying and can disrupt tasks like reading or clicking.
- Usability: A jumpy page makes it difficult to interact with and can lead to accidental clicks.
- Credibility: A visually unstable website can appear unprofessional and untrustworthy.
How Does CLS Affect SEO?
Google uses Core Web Vitals, including CLS, as a ranking factor. A poor CLS score can negatively impact your website’s visibility in search results. This is because Google wants to prioritize websites that offer a good user experience.
How is CLS Calculated?
CLS is calculated by measuring the movement of unstable elements during page load. The larger the shift and the more elements that move, the higher the CLS score. A score of 0.1 or less is considered good.
What is a Good CLS Score?
- Good: CLS score of 0.1 or less.
- Needs Improvement: CLS score between 0.1 and 0.25.
- Poor: CLS score above 0.25.
How Can I Improve My CLS Score?
- Image Dimensions: Always specify width and height attributes for images and videos.
- Ad Optimization: Reserve space for ads to prevent them from pushing content around.
- Dynamic Content: Load new content below the fold (the visible area of the page) to avoid disrupting the user’s view.
- Web Fonts: Use
font-displaysettings to control how fonts load and prevent layout shifts.
What are Some Common Causes of Poor CLS?
- Images without dimensions: When the browser doesn’t know the size of an image, it leaves a blank space until the image loads, causing other elements to shift.
- Ads and embeds: Ads, iframes, and embeds can push content around as they load if not properly sized.
- Dynamically injected content: Content that loads after the initial page render can cause unexpected shifts.
- Web fonts causing FOIT/FOUT: Flash of Invisible Text (FOIT) or Flash of Unstyled Text (FOUT) can occur when web fonts load, causing layout shifts.
What Tools Can I Use to Measure CLS?
- Google Search Console: Provides a Core Web Vitals report with CLS data.
- PageSpeed Insights: Analyzes your page and provides a CLS score.
- Lighthouse: An open-source tool for auditing web page performance, including CLS.
- Chrome DevTools: Allows you to analyze CLS in real-time.
Conclusion:
Cumulative Layout Shift is a crucial aspect of web performance and user experience. By understanding CLS and taking steps to improve your score, you can create a more stable and user-friendly website, which can lead to better search rankings and increased conversions.
How does CLS affect user experience on mobile devices?
CLS can be particularly disruptive on mobile devices due to smaller screen sizes and touch interactions. Unexpected shifts can lead to accidental clicks and frustration, causing users to abandon the page.
What is the relationship between CLS and page load speed?
While not directly related, a slow page load speed can contribute to a higher CLS score. If elements load slowly or in an unexpected order, it can cause the layout to shift.
Can ads cause Cumulative Layout Shift?
Yes, ads are a common cause of CLS. If ad slots aren’t properly sized or if ads load slowly, they can push content around and disrupt the layout.
How can I prevent images from causing layout shifts?
Always include width and height attributes for your images in the HTML code. This allows the browser to reserve space for the image while it loads, preventing shifts.
What is the impact of CLS on accessibility?
CLS can negatively impact accessibility for users with disabilities, especially those using screen readers or assistive technologies. Unexpected layout shifts can make it difficult to navigate and understand the content.
How can I use Google Search Console to monitor my CLS?
The Core Web Vitals report in Google Search Console provides data on your website’s CLS performance, including historical data and trends.
What are some best practices for minimizing CLS in web design?
Use a consistent font size, avoid inserting content above existing content, and preload important resources like fonts and images to reduce layout shifts.
How can I test my website for CLS issues?
Use tools like PageSpeed Insights, Lighthouse, or Chrome DevTools to analyze your website’s CLS and identify potential issues. You can also manually test your website on different devices and browsers.