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C
Performance

Core Web Vitals

Core Web Vitals are Google's user-centered metrics for loading performance, responsiveness, and visual stability: LCP, INP, and CLS.

Core Web Vitals are Google's user-centered metrics for loading performance, responsiveness, and visual stability: LCP, INP, and CLS. Optimization becomes meaningful when real-user data, repeatable lab tests, and an explicit performance budget are used together. The concept is closely related to Largest Contentful Paint and Cumulative Layout Shift.

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Largest Contentful Paint

Cumulative Layout Shift

Interaction to Next Paint

Real User Monitoring

FAQ

Core Web Vitals

How can Core Web Vitals be monitored continuously?
Through real-user monitoring and public field data such as the Chrome User Experience Report, supplemented by automated lab tests on every deployment and a fixed performance budget. Regressions then surface early, for example after new scripts or images. One-off optimizations fade when changes are not checked against thresholds.
Which measures typically improve Core Web Vitals?
For LCP, optimized images and early loading of the main element help; for CLS, fixed placeholders for images, ads, and fonts; for INP, fewer and shorter JavaScript tasks. The weakest metric should be identified first using field data. Generic checklists without measurement often waste effort.
How do field data and lab data differ for Core Web Vitals?
Field data comes from real visitors with their own devices and networks, while lab data comes from repeatable test runs under fixed conditions. Core Web Vitals are assessed on field data. Lab tests suit debugging and before-and-after comparisons but do not reflect the spread of real usage.
Do Core Web Vitals influence rankings?
Google uses them as page experience signals, but relevant content still outweighs them. The effect is hard to isolate; with comparable content, user experience can tip the balance. Good scores mainly improve how the page is used, and no ranking promise can be derived from them.
What did INP replace in Core Web Vitals?
Interaction to Next Paint replaced First Input Delay as the responsiveness metric in March 2024. Unlike FID, INP considers interactions across the entire visit, not just the first. Sluggish menus or forms later in the session therefore also affect the assessment.
What values count as good Core Web Vitals?
LCP up to 2.5 seconds, INP up to 200 milliseconds, and CLS up to 0.1 count as good. Each is assessed at the 75th percentile of field data, meaning the value that three quarters of page views meet or beat. A single lab run is not sufficient for this classification.