Core Web Vitals
What is CLS?
Cumulative Layout Shift measures unexpected movement on the page. It catches moments where text, buttons, images, ads, or banners move after a visitor has started reading or tapping.
Plain-English version
How much content jumps around during loading.
Target
Under 0.1
CLS thresholds
Use thresholds as a triage tool. Field data matters most when there is enough real Chrome traffic for the page.
Good
≤ 0.1
Needs work
0.1–0.25
Poor
> 0.25
Why it matters
What a visitor feels when CLS is bad.
Why CLS matters
Layout shift makes pages feel broken. It can cause visitors to tap the wrong button, lose their place, or distrust a checkout or signup flow.
What a poor result usually means
A poor CLS score usually means images or embeds do not reserve space, fonts swap late, ads inject above content, or banners appear after the layout has already settled.
nimo audit lens
How nimo reads CLS in an audit.
The glossary explains the metric. The free audit checks the page, separates field data from lab diagnostics, and points at the first review step.
How nimo interprets it
nimo reads CLS as visual stability risk. One late banner, ad, image, embed, or font swap can create most of the score.
Source to trust first
Trust CrUX field data for impact when it exists. Use Lighthouse screenshots and traces to find shifts reproduced in lab.
Evidence to inspect
- The shifted elements and when they moved.
- Images, videos, ads, or embeds without reserved space.
- Cookie banners, promo bars, or injected content above existing content.
- Font loading and mobile template differences.
First fix to review
Reserve stable space for the element that moves before changing unrelated scripts or styles.
How to validate
Rerun mobile and desktop audits and confirm the shifted element is gone, then monitor field CLS for the affected URL group.
What to fix first
Do not chase the score. Fix the bottleneck.
The right fix depends on the metric, the page template, and whether the issue appears in real visitor data.
- Set width and height or aspect-ratio for images and videos.
- Reserve stable space for ads, embeds, cookie banners, and promo bars.
- Use font-display carefully and preload critical fonts.
- Avoid inserting content above existing content after load.
- Check mobile templates separately from desktop templates.
How nimo helps
Run the free audit, then ask: “What is causing layout shift on my page?”
nimo flags layout instability in the context of the page and explains which template or element is most likely causing the shift.
No signup needed. Takes about 30 seconds.