Definition

Lighthouse is an open-source, automated auditing tool that evaluates a web page and produces a report across categories including performance, accessibility, SEO and general best practices. Each audit explains what was measured and offers guidance on addressing issues found.

Lighthouse can be run from Chrome DevTools, a Node command-line interface, a Node module for use in continuous integration, or through PageSpeed Insights. Its performance category produces lab data — measurements taken in a controlled, simulated environment rather than from real users — which can differ from field data collected through the Chrome User Experience Report. Metrics it reports include First Contentful Paint, Largest Contentful Paint, Cumulative Layout Shift and Total Blocking Time.

Examples

• Developer workflow

  A developer opens the Lighthouse panel in Chrome DevTools and runs an audit on a landing page, then works through the flagged performance and accessibility issues.

• Continuous integration

  A team adds the Lighthouse Node module to its build pipeline so that a performance score is recorded for every deployment.

Sources

• Chrome for Developers — Lighthouse overview
• Google Search Central — Page experience

Related terms

• Core Web Vitals
  A set of three Google metrics that measure real-world page experience: loading speed, interactivity and visual stability.
• Page Speed
  How quickly a web page loads and becomes interactive, measured by metrics such as Largest Contentful Paint, Interaction to Next Paint, and Time to First Byte.
• Page Experience
  Google's umbrella term for signals describing how users perceive a page — Core Web Vitals, HTTPS, mobile usability, and absence of intrusive interstitials.
• PageSpeed Insights
  A Google tool that reports a web page's performance on mobile and desktop using both real-user field data and simulated lab data.
• Total Blocking Time
  A lab metric that sums how long the browser's main thread was blocked by long tasks after First Contentful Paint.
• Largest Contentful Paint
  A Core Web Vitals metric measuring how long the largest visible content element on a page takes to render after loading begins.
• Cumulative Layout Shift
  A Core Web Vitals metric measuring how much visible content unexpectedly shifts position during the lifetime of a page.

Where QueryCatch uses this

• SEO Audit
• Page Optimisation