---
language: en
title: "CLS: Cumulative Layout Shift"
description: "CLS measures unexpected shifts of visible elements on a page. Learn about the visual stability score and how to investigate changes during use."
canonical: "https://tropk.ai/en/resources/glossary/cls-cumulative-layout-shift"
last_modified: "2026-10-12T16:09:16.988Z"
---

# CLS: Cumulative Layout Shift

Reviewed on 2026-10-07.

## What it means

CLS stands for Cumulative Layout Shift. It is a visual stability metric that considers unexpected changes in the position of visible page elements. The value is the largest sum of scores in a session of closely spaced shifts, lasting up to five seconds. As a Core Web Vital, it helps show how much the layout changes during the user experience.

## Why it matters for marketing

For marketing, CLS helps investigate pages where reading or taking action is interrupted by unexpected movement. A promotional banner that appears late may push a button while someone is trying to click it. The team can report the issue as element instability rather than describing it only as a feeling of slowness. The problem may persist even when images load quickly.

## Example in practice

Imagine a school whose enrollment page loads a notice above the form after a few seconds. The focused field changes position, and the person loses their place while reading. The team reproduces the load, identifies the shift, and requests reserved space for the notice. They then check stability with the same delay, without assuming that removing all movement is the solution.

## How to apply or check

Observe the page during loading and after interactions and content insertions. Record the elements that shift and related resources, such as images, fonts, and external components. web.dev recommends a CLS of up to 0.1 at the 75th percentile of visits, separated by device. Lab tests help locate causes; real-world data may reveal shifts that are absent from an initial capture.

## Important distinctions

CLS is a score with no unit of time, not milliseconds or a percentage of visitors. Not every visual change counts toward the calculation: shifts near certain user actions may be excluded. The value does not indiscriminately add up all movements during a visit. A low score also does not certify reading comfort or accessibility; these issues require observing the content and navigation.

## Sources and references

- [Cumulative Layout Shift (CLS)  |  Articles  |  web.dev](<https://web.dev/articles/cls>) — Google / web.dev

## Continue a leitura

- [Core Web Vitals](</en/resources/glossary/core-web-vitals>)
- [INP: Interaction to Next Paint](</en/resources/glossary/inp-interaction-to-next-paint>)
- [LCP: Largest Contentful Paint](</en/resources/glossary/lcp-largest-contentful-paint>)

## About the author

[Vinicius Pacheco](</en/team/vinicius-pacheco>)

Responsible for Tropk’s technical content, focusing on crawling, indexing, structured data, and agent access to content.

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