A metric measuring how much a page's visible content unexpectedly moves during loading.
ID
SS-DF-036
Confidence
High · 88
Evidence
Strong
Updated
2026-07-08
Definition
A metric measuring how much a page's visible content unexpectedly moves during loading.
Cumulative Layout Shift (CLS) quantifies visual stability by summing the unexpected movement of visible elements as a page loads, expressed as a unitless score. A good CLS is 0.1 or less, and high scores frustrate users when buttons or text jump just as they interact. Common causes include images and ads without reserved dimensions, late-loading fonts and content injected above existing elements.