What Is CLS (Cumulative Layout Shift)?
Updated 6 October 2026
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Cumulative Layout Shift (CLS) measures how much the visible content of a page jumps around unexpectedly during a visit. It is one of the three Core Web Vitals, and unlike the other two it is a score, not a time. Google rates a CLS of 0.1 or less as good, and anything over 0.25 as poor, measured at the 75th percentile of real visits.
What does CLS actually measure?
CLS measures visual stability, the amount that on-screen elements move without the visitor causing it. Every time a button, image, or paragraph shifts position after it was already visible, the page records a layout shift.
The score is unitless. It combines how much of the screen moved with how far it moved, then reports the worst burst of shifts during the visit as one number.
Shifts that follow a visitor's own action within a fraction of a second do not count. Opening a menu you tapped is expected, but content that slides down on its own while you are reading is the problem CLS captures.
What counts as a good CLS score?
A good CLS is 0.1 or less, and Google treats anything over 0.25 as poor. The band in between needs improvement. All three ratings are read at the 75th percentile, so at least three quarters of your page views must score 0.1 or less to rate good.
| Rating | CLS (75th percentile) |
|---|---|
| Good | 0.1 or less |
| Needs improvement | 0.1 to 0.25 |
| Poor | Over 0.25 |
Source: web.dev, Cumulative Layout Shift (Google, 2026).
Because CLS is a score and not a time, it has no seconds or milliseconds. A lower number means a steadier page, and zero means nothing moved unexpectedly.
Why does my page shift around?
Layout shifts usually come from content that arrives late and pushes everything below it. The browser lays out the page, then something loads and the layout has to move to fit it in.
- Images without set dimensions. If the browser does not know a photo's size, it reserves no space, then shoves the text down when the image arrives.
- Ads, embeds, and iframes with no reserved space. A booking widget or social feed that loads late drops in and pushes the rest of the page.
- Web fonts that swap. Text first shows in a fallback font, then reflows when the custom font loads, nudging lines around.
- Content injected at the top. A cookie notice or promo bar added after load moves everything beneath it downward.
The common fix is to reserve space in advance. Setting width and height on images, giving ad slots a fixed size, and loading fonts carefully all stop the page from rearranging itself under the visitor.
How does CLS relate to the other Core Web Vitals?
CLS is the visual-stability metric of the three, and each of the others measures a different part of the experience. They are scored separately, so a page can pass one and fail another.
| Metric | What it measures |
|---|---|
| LCP | Loading: when the main content appears |
| INP | Interactivity: response to taps and clicks |
| CLS | Visual stability: unexpected layout shifts |
A page that loads its hero fast and responds quickly to taps can still fail a shopper if the "Buy" button jumps just as they reach for it. That is why Google reports all three together.
Frequently asked questions
Is CLS a Google ranking factor?
Yes. Google says Core Web Vitals are used by its ranking systems, and CLS is one of them. Google still shows the most relevant content first, even when page experience is weak. A stable page helps most when many pages answer the query equally well. It is not a substitute for useful content, and it will not rescue a page that answers the wrong question.
What is a good CLS score?
A good CLS is 0.1 or less at the 75th percentile of visits. Between 0.1 and 0.25 needs improvement, and over 0.25 is poor. Because the score has no unit, treat 0.1 as your ceiling and aim below it so normal variation does not tip you over.
Why is CLS a score instead of a time?
CLS measures movement, not speed, so seconds would not describe it. Each shift's score multiplies how much of the screen shifted by how far it moved. CLS then reports the largest burst of shifts in the visit, not a running total. A bigger, further jump adds more to the number than a small nudge.
What is the most common cause of a bad CLS?
Images and ads without reserved space are the usual culprits. When the browser does not know how much room an element needs, it lays out the page without it, then jolts everything down when it finally loads. Setting explicit sizes fixes most of these cases.
Can a layout shift ever be acceptable?
Yes. A shift that happens within about half a second of a visitor's own tap or click is treated as expected and does not count toward CLS. Opening an accordion you clicked is fine. Only movement the visitor did not ask for hurts the score.
Where CLS fits your site
Storming Solutions builds and maintains websites for Malaysian businesses from Kuala Lumpur. Layout stability is one of the quieter things we check on a site that looks fine but feels awkward to use. In our experience maintaining Malaysian SME sites, stability slips as banners, embeds, and images are added over the years without space reserved for them.
Want to know if your pages are shifting under your visitors? Ask us on WhatsApp and we will run the check as part of a free website review, then point you to the element that moves most.