Technical SEO
What is CLS (Cumulative Layout Shift)?
CLS measures how much elements shift unexpectedly during load — target: < 0.1. Penalizes "jumpy" UIs.
CLS (Cumulative Layout Shift) is the 3rd Core Web Vital. Its target is < 0.1; > 0.25 is bad. It penalizes sites that load, and when the user tries to click a button, it shifts (lazy-loaded ad, font swap, image without dimensions).
Main fixes: explicit width/height on images (don't make the browser guess), aspect-ratio on embeds, font-display: optional or font preload, and never insert content above already-rendered content.
Formula
Bom: ≤ 0,1 · Pode melhorar: 0,1–0,25 · Ruim: > 0,25Use it in practice
SEO Analyzer
Frequently asked questions
How to avoid CLS from fonts?
Use font-display: optional or swap + font preload; otherwise, font flips from fallback to loaded, and everything shifts.
Does CLS count user interactions?
No. Shift caused by user click (open modal, expand accordion) is excluded from CLS — only "unexpected" counts.