What Cumulative Layout Shift (CLS) means
Layout shifts make people tap the wrong button or lose their place. Common causes are images without set dimensions, late-loading ads and fonts that swap. These are usually simple to fix once identified.
Why it matters for your website
When buttons and text jump around, visitors tap the wrong thing, lose their place and get annoyed. Layout shift is one of Google's Core Web Vitals, so a poor score can also count against your page experience in search. On a lead form or checkout page, a sudden shift can be the difference between a submitted form and a lost customer.
Example
A plumber's homepage loads its phone number, then a late banner image pushes it down just as a visitor tries to tap it. Reserving space for the banner stops the jump.
Tips
- Set width and height on images and videos so the browser reserves space before they load.
- Reserve fixed space for ads, embeds and cookie banners instead of letting them push content.
- Check the field data in Search Console's Core Web Vitals report, not just one lab test.
Common mistakes
- Injecting promo bars or pop-ups above existing content after the page has started loading.
- Loading custom web fonts in a way that makes text reflow noticeably when they arrive.
Questions about Cumulative Layout Shift (CLS)
What is Cumulative Layout Shift (CLS)?
A score for how much page content unexpectedly jumps around while loading. Good is 0.1 or less.
How do I find what is causing layout shift on my page?
Run the page through PageSpeed Insights or Chrome DevTools, which highlight the elements that moved. Images without set dimensions, late ads and font swaps are the usual causes.
Does layout shift that happens after I click count against me?
Generally no. Shifts that happen right after a user interaction, like opening a menu, are expected and excluded from the score.
