Performance
LCP
Largest Contentful Paint
Largest Contentful Paint (LCP) measures the time from navigation start until the largest visible element on the screen finishes rendering. It is one of three Core Web Vitals and the primary perceived-loading metric.
In depth
The largest element is usually a hero image, a poster video, or a large block of text. LCP is sensitive to slow servers (high TTFB), render-blocking JavaScript and CSS, large unoptimised images, and lazy-loading the hero image (which delays its discovery).
Google's official thresholds are: Good ≤ 2.5 s, Needs Improvement 2.5–4.0 s, Poor > 4.0 s. The 75th percentile across real users is what counts for ranking.
Why it matters
LCP is the easiest Core Web Vital to fix — preload the LCP image, serve it as WebP/AVIF at the right size, eliminate render-blocking resources, and put your origin behind a CDN. Improvements show up in field data within 28 days.
How Lemwatch helps with lcp
Lemwatch monitors lcp continuously and alerts you the moment something changes.
Performance monitoring →Related terms
Core Web Vitals
Core Web Vitals are a set of three Google-defined metrics that measure real-user experience on a webpage: Larg…
TTFB
Time To First Byte (TTFB) measures how long after a request before the first byte of the response arrives. It …
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, …
Real User Monitoring
Real User Monitoring (RUM) captures actual page load performance in real visitors' browsers — LCP, INP, CLS, T…
Browse the full Lemwatch monitoring glossary (47 terms).