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.
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
Ask nimo: “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.