What it is
Core Web Vitals are a small set of user-centered performance signals covering loading, interaction responsiveness, and visual stability: LCP, INP, and CLS.
Mental model
Use the metrics as smoke alarms. They reveal categories of user friction, then diagnostics and product context identify the actual cause and worthwhile fix.
Why it exists
A shared set of field metrics helps teams and tools discuss important parts of page experience consistently across sites.
When to use it
- Monitoring real-user performance over time
- Finding page types or cohorts with degraded experience
- Setting performance budgets alongside product context
When not to use it
- Do not optimize a score while ignoring the actual interaction
- Do not assume one lab run represents the user population
Production considerations
- Prioritize field data when enough traffic exists
- Segment by route, device, geography, and release
- Connect regressions to deploys and ownership
Accessibility implications
Stable, responsive pages reduce cognitive and motor barriers. Performance work should preserve zoom, motion preferences, semantics, and content access.
Performance implications
The metrics are outputs, not direct fixes. Improve them by addressing the specific loading, main-thread, rendering, or layout behavior behind the measurement.