Performance
Core Web Vitals
CWV
Core Web Vitals are a set of three Google-defined metrics that measure real-user experience on a webpage: Largest Contentful Paint (LCP), Interaction to Next Paint (INP), and Cumulative Layout Shift (CLS). They are direct Google ranking signals.
In depth
LCP measures loading performance — how long before the largest visible element renders. Good is under 2.5 seconds. INP measures responsiveness — the longest interaction delay during the page session. Good is under 200 ms. CLS measures visual stability — how much page content shifts after first render. Good is under 0.1.
Core Web Vitals are measured both in the lab (via Lighthouse / PageSpeed Insights) and in the field (via the Chrome User Experience Report — CrUX — which only counts real Chrome users on real devices). Field data is what Google uses for ranking.
Why it matters
Core Web Vitals are part of Google's Page Experience ranking algorithm and directly affect organic search position, especially in competitive verticals. They also correlate strongly with conversion rate — every 100 ms of LCP improvement typically lifts revenue by 1-2% on e-commerce sites.
How Lemwatch helps with core web vitals
Lemwatch monitors core web vitals continuously and alerts you the moment something changes.
Performance monitoring →Related terms
LCP
Largest Contentful Paint (LCP) measures the time from navigation start until the largest visible element on th…
CLS
Cumulative Layout Shift (CLS) measures how much visible content unexpectedly moves around the page during load…
INP
Interaction to Next Paint (INP) measures the longest single-interaction latency a user experiences on a page, …
TTFB
Time To First Byte (TTFB) measures how long after a request before the first byte of the response arrives. It …
Lighthouse
Lighthouse is Google's open-source automated auditing tool for web pages. It produces a 0-100 score across per…
Browse the full Lemwatch monitoring glossary (47 terms).