Core Web Vitals: What Google Is Actually Measuring and Why It Matters

Yes, since May 2021, Core Web Vitals have been a confirmed ranking factor in Google's Page Experience signals. However, the weight is modest — Google has stated that content relevance still matters far more than page experience signals. Sites with poor Core Web Vitals won't necessarily tank in rankings if their content is highly relevant, but all else being equal, good CWV scores help. The more significant effect is indirect: poor performance increases bounce rates, and high bounce rates signal to Google that users aren't finding what they want — which does affect rankings.

Google defines three tiers: Good, Needs Improvement, and Poor. For LCP: Good is under 2.5 seconds, Needs Improvement is 2.5–4 seconds, Poor is over 4 seconds. For INP: Good is under 200 milliseconds, Needs Improvement is 200–500ms, Poor is over 500ms. For CLS: Good is under 0.1, Needs Improvement is 0.1–0.25, Poor is over 0.25. The goal is 'Good' on all three metrics for at least 75% of page loads. Google's Search Console shows field data (real user measurements) which are what actually count for rankings, not just lab measurements from Lighthouse.

Lighthouse is a lab measurement tool — it tests your page in a controlled simulated environment. Core Web Vitals in Google Search Console are field data — actual measurements from real users in their real environments, on their real devices and connections. These often differ significantly. Lighthouse might show LCP of 1.8s on a fast laptop. Your GSC field data might show 4.2s because many of your users are on mid-range Android phones on mobile networks. Rankings use field data. Use Lighthouse for diagnosing specific issues, but don't confuse Lighthouse scores with your actual Core Web Vitals ranking signals.