Have you ever been on a website, about to click on something, and suddenly everything shifts, causing you to click on the wrong link or button? Annoying, right? If you’ve experienced this, you’ve come face to face with something called Cumulative Layout Shift, or CLS. It’s more than just a nuisance; it’s a significant factor in SEO that dictates how user-friendly and accessible your website is.
Today, we’re going to unpack CLS and why it matters for your site’s SEO. We’ll go over what CLS is, how it affects your website’s performance, and what you can do to minimize its impact. By the end, you’ll have a clear picture of why keeping CLS in check isn’t just about user experience—it’s also about securing your place in search engine results. Let’s get started!
What Exactly is Cumulative Layout Shift?
To put it simply, Cumulative Layout Shift measures the instability of content on your web pages. It’s one of Google’s Core Web Vitals, which are a set of metrics designed to assess the health of a website’s user experience. CLS specifically looks at how much your page elements move around while the page is loading.
Imagine you’re reading an article online. As you scroll down, an image above suddenly loads and pushes the text you were reading further down. This unexpected movement is what CLS is all about. It’s calculated by measuring the distance and impact of these shifts, giving each page a score based on its overall stability.
Why Does CLS Happen?
There are a few common culprits behind layout shifts:
- Images without dimensions: When images don’t have specified height and width values in the HTML or CSS, they can cause the layout to shift as they load.
- Ads and embeds: These elements can load asynchronously and disrupt your content unless you reserve space for them.
- Dynamic content: Content that changes size or position while loading can lead to layout shifts.
Understanding these causes is the first step in addressing CLS issues. By identifying and fixing these elements, you can create a smoother, more reliable user experience.
How CLS Affects SEO
Now, why should you, as an SEO enthusiast, care about all this? Well, Google considers CLS as part of its Page Experience update. This means that a high CLS score can directly impact your rankings on search engine results pages (SERPs). Google aims to prioritize websites that offer a good user experience, and a stable layout is a significant part of that.
Consider this: if users frequently experience unexpected shifts on your site, they might get frustrated and leave. This can lead to higher bounce rates, lower engagement, and ultimately, reduced visibility in search results. So, a low CLS score isn’t just a technical concern; it’s a business one.
The User Experience Connection
While SEO focuses on getting people to your site, user experience is about keeping them there. When users find a site easy to navigate, they’re more likely to stay longer, explore more pages, and even come back. CLS ties directly into this because unexpected layout shifts can disrupt the flow of your site and deter users from continuing their journey.
By reducing CLS, you’re not only optimizing for search engines but also showing your audience that you value their time and experience. This can lead to improved customer satisfaction, increased trust, and potentially more conversions.
Measuring CLS: The Tools You Need
Before you can fix CLS issues, you need to measure them. Thankfully, there are several tools at your disposal:
- Google PageSpeed Insights: This tool provides a detailed analysis of your site’s performance, including a breakdown of your Core Web Vitals like CLS.
- Lighthouse: Available in Chrome DevTools, Lighthouse offers a comprehensive report on how your site performs, complete with suggestions for improvement.
- Web Vitals Extension: This Chrome extension gives you real-time feedback on your site’s Core Web Vitals, so you can see how changes affect your CLS immediately.
Using these tools, you can get a clear picture of which pages on your site are underperforming and prioritize them for optimization. Each tool offers a slightly different perspective, so using a combination can give you the most comprehensive view.
Interpreting CLS Scores
Once you have your data, the next step is to interpret it. CLS is scored on a scale from 0 to 1, with scores closer to 0 indicating better stability. Here’s a quick guide:
- Good: A score of 0.1 or less means your page is stable and user-friendly.
- Needs Improvement: Scores between 0.1 and 0.25 suggest there’s room for improvement.
- Poor: Anything above 0.25 indicates significant layout shift issues that need to be addressed.
Understanding these thresholds will help you prioritize which pages need immediate attention and which ones can wait.
Common Causes of High CLS and How to Fix Them
Once you’ve identified pages with high CLS scores, it’s time to roll up your sleeves and start fixing them. Here are some common issues and how to resolve them:
Images Without Dimensions
One of the biggest offenders is images that don’t have set dimensions. Without specific height and width attributes in your HTML or CSS, the browser doesn’t know how much space to reserve for the image, causing the layout to shift when it finally loads.
Solution: Specify dimensions for all your images. This way, the browser can allocate the right amount of space as the page loads, preventing unexpected shifts.
Ads and Embeds
Ads and embedded content can be tricky because they often load after the main content. If they don’t have reserved space, they can push everything around.
Solution: Use CSS to allocate space for ads and embeds, even before they load. This helps keep everything in place, regardless of when these elements appear.
Web Fonts and Dynamic Content
Web fonts can also cause shifts, especially if they load slowly or replace a fallback font. Similarly, dynamic content like interactive elements or animations can disrupt your layout.
Solution: Use font-display: swap; in your CSS to ensure text remains visible during font loading. For dynamic content, reserve space and ensure animations are smooth and predictable.
CSS Tricks to Improve CLS
CSS is your friend when it comes to optimizing CLS. Here are a few tricks you can use:
- Minimize animations: Avoid animations that affect layout, like those changing size or position. If necessary, use transform and opacity properties, as they don’t trigger layout recalculations.
- Use aspect-ratio: This CSS property helps maintain a consistent aspect ratio for images and videos, preventing shifts as they load.
- Preload important resources: By preloading key resources, you can ensure they load quickly and reduce the likelihood of shifts.
These CSS strategies can make a significant difference in how your page stabilizes as it loads, helping you achieve a lower CLS score.
JavaScript Solutions for Better CLS
JavaScript can also play a role in managing CLS. Here’s how:
Defer Non-Essential Scripts
Scripts that are not crucial for the initial content can be deferred. This means they won’t delay the loading of the main content, reducing the chance of layout shifts.
Solution: Use the defer attribute in your script tags for non-essential scripts. This ensures they load after the HTML parsing, keeping your layout stable.
Control Dynamic Content Loading
JavaScript often controls dynamic content, which can be a major source of shifts. Controlling when and how this content loads can mitigate these issues.
Solution: Use JavaScript to dynamically allocate space for content before it loads. This can be as simple as setting a placeholder element with the expected dimensions.
By incorporating these JavaScript strategies, you can further refine your website’s user experience and minimize layout shifts.
Case Studies: Learning from Real-World Examples
Let’s take a look at some real-world examples of how businesses have tackled CLS and improved their SEO as a result:
Case Study 1: The Online Retailer
An online retailer noticed high bounce rates on their product pages. After investigating, they discovered that images were loading slowly and causing significant shifts. By optimizing image dimensions and preloading important resources, they reduced their CLS score significantly. As a result, they saw an increase in time spent on the site and a decrease in bounce rates.
Case Study 2: The News Website
A news website was experiencing issues with ads that loaded unpredictably. They implemented CSS solutions to reserve space for ads and used JavaScript to control when dynamic content appeared. These changes improved their CLS score and led to higher engagement rates, as users could read articles without interruption.
These examples show that addressing CLS isn’t just a technical exercise; it’s a practical way to improve user experience and ultimately, business outcomes.
Ongoing Maintenance: Keeping Your CLS Score Low
Once you’ve tackled your initial CLS issues, it’s important to maintain your scores. Here’s how you can keep things in check:
- Regular audits: Schedule regular audits of your website’s Core Web Vitals. This will help you catch new issues before they affect your users.
- Monitor updates: Keep an eye on updates to your CMS, plugins, and any third-party content. Changes to these can inadvertently introduce shifts.
- Stay informed: SEO and user experience best practices evolve constantly. Stay informed about the latest developments to ensure your site remains optimized.
By treating CLS as an ongoing project rather than a one-time fix, you can maintain a stable, user-friendly site that performs well in search rankings.
Final Thoughts
CLS might seem like just another metric at first glance, but it plays a crucial role in the overall user experience and SEO performance of your website. By understanding what it is, why it matters, and how to manage it, you’re taking a big step toward creating a site that’s both user-friendly and search engine-friendly.
And if you’re looking for expert help, consider working with Pattern. We specialize in helping ecommerce brands and SaaS startups grow by driving meaningful traffic from Google and converting that traffic into paying customers. Our approach isn’t just about rankings; it’s about delivering real results. Whether it’s creating programmatic landing pages or crafting content that converts, we view SEO as part of a bigger growth strategy, ensuring every dollar you invest delivers tangible ROI. If you’re ready to make SEO a powerful growth channel, let’s work together.