Core Web Vitals

What is Core Web Vitals?

Core Web Vitals are three field metrics Google uses to score how a page actually behaves for real users, separate from how it performs in a synthetic test. The current trio is Largest Contentful Paint, which measures loading speed, Interaction to Next Paint, which measures responsiveness, and Cumulative Layout Shift, which measures visual stability. Each metric has clear thresholds for "good," "needs improvement" and "poor," and pages that hit "good" on all three earn a small but persistent ranking boost.

Largest Contentful Paint (LCP): Good if under 2.5 seconds, measures perceived load speed

Interaction to Next Paint (INP): Good if under 200 milliseconds, measures responsiveness

Cumulative Layout Shift (CLS): Good if under 0.1, measures visual stability during load

Source: Real-world Chrome User Experience Report (CrUX) data, not lab tests

Why does Core Web Vitals matter?

Core Web Vitals matter because they translate vague "site speed" advice into specific, measurable thresholds tied to ranking. A page that loads fast in the lab can still fail real-world Core Web Vitals if the user's network, device or third-party scripts drag it down. Brand teams investing in content quality should also track Core Web Vitals, since a poor score can wipe out the gains from better writing by sinking the page's overall ranking ceiling.

How do you use Core Web Vitals?

1. Pull your real-world Core Web Vitals scores from Google Search Console's Page Experience report or directly from CrUX, not just from Lighthouse lab tests.

2. Prioritize fixes by impact: a page that fails LCP at the 75th percentile usually delivers more lift than chasing marginal CLS gains.

3. Monitor Core Web Vitals weekly after major releases, since a single new third-party script or hero image swap can swing scores hard.