Introduction to CLS
Cumulative Layout Shift (CLS) is one of the three Core Web Vitals and a key measure of how visually stable your site feels. At Uxify, we use CLS as a critical checkpoint for diagnosing disruptive layout shifts during page load and interaction.
CLS captures how much visible content moves around the screen unexpectedly. This could be a button jumping out of place or a headline shifting as fonts load. These shifts are not just annoying - they directly impact user trust and experience.
Healthy CLS
To deliver a stable experience, the 75th percentile (P75) of Cumulative Layout Shift (CLS) should be under 0.1. This means 75% of your real users experience minimal layout shift. Below is how Uxify categorizes CLS performance:
LCP Range | Status |
0 – 0.05 | Excellent |
0.05 – 1 | Good |
1 – 0.25 | Needs Improvement |
0.25 and above | Poor |
How CLS matters
Two words: users and Google. Let’s start with your users. Ever tried to tap a button, only for it to shift at the last second and cause a misclick? That’s CLS at work - and it frustrates users more than you'd expect. A low CLS makes your interface feel stable and polished, which builds trust and improves conversions.
Then there's Google. CLS is part of its Core Web Vitals scoring, meaning it's baked right into how search rankings are influenced. A jittery, unstable layout can lower your credibility - and your visibility. So yes, fixing CLS is about looking good and being found.
Top 3 reasons for failing CLS
Here are three of the most common and actionable reasons we see for high CLS in Uxify Experience:
Unreserved space for dynamic content
A common offender: images, ads, or embeds loading without reserved dimensions. When content is injected without telling the browser how much space to leave, everything shifts. You can easily detect this in the following Uxify CLS lenses: CLS breakdown, CLS by element.
Web fonts causing shifts
When web fonts load late and cause text to reflow, it’s called a Flash of Unstyled Text (FOUT). This can cause measurable layout instability.
Third-parties
Widgets like chat bubbles, pop-ups, or review badges can inject unpredictability into your layout. Use these Uxify lenses to track them: CLS breakdown, CLS by third party, CLS by cookie name
You can use 80+ CLS lenses in Uxify Experience to find your website’s top layout offenders. It’s all displayed in a single dashboard view, so you can spot patterns instantly. Once identified, you can stabilize your layout and eliminate shift anxiety using Navigation AI.