---
type: Glossary Term
title: "Cumulative Layout Shift (CLS)"
description: "How much visible content unexpectedly shifts during a page lifetime."
resource: "https://prerendering.com/glossary/cls"
tags: [metrics, glossary]
timestamp: 2026-05-11T00:00:00Z
---

# Cumulative Layout Shift (CLS)

How much visible content unexpectedly shifts during a page lifetime.

A Core Web Vital. Measures the sum of all unexpected layout shifts during the lifespan of the page. Good < 0.1, needs improvement 0.1-0.25, poor > 0.25. Common causes: images without dimensions, late-loaded fonts, ad slots, banners that inject after first paint.

Also known as: CLS.

## Related

- [Core Web Vitals Optimization for Engineering Teams](/blog/core-web-vitals-for-engineering-teams.md)