Advanced – Non-Functional Testing
Cumulative Layout Shift (CLS) – ISTQB Definition
Last Updated: July 12, 2026 · SoftwareTestPilot QA Team
Official ISTQB Definition
A Core Web Vital measuring the total amount of unexpected layout shift during page load.
In simple words
How much the page jumps around while loading.
Exam tip
Target: CLS under 0.1. Caused by images without dimensions, injected ads, late-loading fonts.
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