KnowledgeSEO & Search / Metric explained
Cumulative Layout Shift
CLS · How much page content unexpectedly jumps around while someone uses it.
The metric, at your level
Understand CLS in context.
Simply explained explanation
How much page content unexpectedly jumps around while someone uses it.
Professional explanation
Core Web Vital summarizing unexpected visual instability during the page lifetime.
Analytical explanation
Investigate images without dimensions, delayed banners, font swaps and inserted widgets. Look for shifts affecting buttons and checkout fields.
Technical explanation
CLS is unitless. The “good” threshold is ≤0.1 at the 75th percentile of field experiences; scores capture unexpected layout shifts.
Four complementary explanations — choose your level. Technical definitions are platform-specific where noted.
Calculation / definitionUnitless layout instability score
↗ How to use it
Reserve space for media and dynamic UI.
⚠ Common interpretation mistake
CLS is not measured in pixels.