Definition

Largest Contentful Paint (LCP) is a Core Web Vitals metric that measures the time from the start of page load until the largest visible image, video poster, or block of text in the viewport finishes rendering.

Google's published thresholds, measured at the 75th percentile of page loads in the field, are "good" ≤2.5s, "needs improvement" ≤4.0s, and "poor" >4.0s. The element treated as the LCP element is recalculated as the page loads — only elements visible in the initial viewport are eligible. LCP is reported in Google's CrUX dataset, the PageSpeed Insights tool, the Search Console Core Web Vitals report, and via the web-vitals JavaScript library.

Examples

• Slow hero image on a homepage

  A news site's homepage hero image weighs 1.2 MB. CrUX field data records an LCP of 4.5 seconds at the 75th percentile — the "poor" bucket. After serving a smaller, preloaded version, LCP drops to 2.1 seconds and moves into "good".

Sources

• web.dev — Largest Contentful Paint (LCP)

Related terms

• Core Web Vitals
  A set of three Google metrics that measure real-world page experience: loading speed, interactivity and visual stability.
• Lazy Loading
  A technique that defers loading of off-screen images, iframes, or other resources until the user is about to scroll them into view.
• Render-Blocking Resources
  Resources — typically CSS and synchronous JavaScript — the browser must fetch and parse before it can paint the first frame of a page.

Where QueryCatch uses this

• Page Optimisation
• Image Optimisation