How to Set an Explicit Width and Height on Image Elements to Reduce Layout Shifts and Improve CLS in Webflow

In the world of web design, user experience is paramount. One key metric for measuring this is the Cumulative Layout Shift (CLS), which gauges the visual stability of a webpage. High CLS can lead to poor user experience, as elements move around unexpectedly while the page loads. One effective way to tackle this issue, particularly in Webflow, is by explicitly setting the width and height for image elements.

Understanding CLS and Its Impact

Cumulative Layout Shift (CLS) is a metric used by Google’s Core Web Vitals to evaluate how stable the content on a page is during loading. A high CLS score indicates that the page experiences significant visual shifts, which can frustrate users. This is particularly problematic on mobile devices, where users expect smooth, stable interactions.

The Role of Explicit Dimensions

When an image is loaded without defined dimensions, the browser doesn’t know how much space to allocate for it on the page. As the image downloads, it can cause content to shift, leading to a higher CLS score. By setting explicit width and height attributes on image elements, you allow the browser to reserve the correct amount of space in advance. This proactive approach prevents unexpected layout changes and improves the overall user experience.

Implementing Explicit Dimensions in Webflow

Webflow offers a visual interface that makes it straightforward to set the dimensions of your images. Here’s how to do it:

1. Select Your Image Element

• In the Designer, click on the image you wish to modify.
• Make sure you have the correct element selected, as changes will apply only to that instance.

2. Set the Width and Height in the Style Panel

• Navigate to the Style Panel on the right-hand side.
• Under the Size section, you’ll see fields for both width and height.
• Enter the explicit values (in pixels, percentages, or other units) that best fit your design. For example, setting the width to 600px and the height to 400px reserves that space in the layout.

3. Check Responsiveness

• Preview your design in different device views (desktop, tablet, mobile) to ensure that the explicit dimensions work well across all breakpoints.
• Adjust as necessary. You might need to use media queries or set different values for various screen sizes to maintain optimal layout stability.

4. Optimize Images for Performance

• While setting explicit dimensions improves layout stability, optimizing your images for web use is equally important. Use Webflow’s built-in image optimization tools or external image compressors to ensure your images load quickly, further reducing potential layout shifts.

Best Practices for Maintaining Low CLS

• Reserve Space for Dynamic Content: For elements that load asynchronously (like ads or third-party widgets), consider using placeholder spaces to prevent sudden shifts.
• Use Aspect Ratio Boxes: Webflow allows you to maintain an aspect ratio for elements. This is especially useful when the image’s dimensions might vary depending on its source or device.
• Test Continuously: Use tools like Google PageSpeed Insights or Lighthouse to monitor your CLS score and identify any elements that might be causing shifts.

Explicitly setting width and height on image elements is a simple yet effective strategy to reduce layout shifts and improve your website’s CLS score. In Webflow, this practice is easily implemented through the Style Panel, ensuring that your design remains stable and visually appealing during page loads. By following these steps and incorporating best practices, you can enhance the user experience and contribute to better SEO and overall site performance.