Understanding LCP, CLS, INP and how to improve them.
Google's Core Web Vitals are the three critical metrics that determine user experience and search ranking impact.
What: How long until the biggest visible element (hero image, heading) loads.
Rating — Threshold —
🟢 Good — ≤ 2.5 seconds —
🟡 Needs work — 2.5–4.0 seconds —
🔴 Poor — > 4.0 seconds —
How to fix: Optimise images (WebP/AVIF), use a CDN, preload critical resources, reduce server response time.
What: How much the page layout shifts unexpectedly while loading.
Rating — Threshold —
🟢 Good — ≤ 0.1 —
🟡 Needs work — 0.1–0.25 —
🔴 Poor — > 0.25 —
How to fix: Set explicit width/height on images and videos, avoid inserting content above existing content, use CSS aspect-ratio.
What: How quickly the page responds to user interactions (clicks, taps, key presses).
Rating — Threshold —
🟢 Good — ≤ 200ms —
🟡 Needs work — 200–500ms —
🔴 Poor — > 500ms —
How to fix: Break up long JavaScript tasks, defer non-critical scripts, use web workers for heavy computation.
LemWatch runs Lighthouse audits on both mobile and desktop viewports. You can compare scores side-by-side on any site's Performance tab, with 7/30/90-day trend charts.
Google uses mobile-first indexing, so mobile scores directly impact your search ranking. Desktop scores matter for user experience on larger screens. LemWatch tracks both independently.