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SEO Glossary

Lighthouse

Definition

Google Lighthouse is an automated, open-source tool that audits web pages for performance, accessibility, best practices, SEO, and Progressive Web App capabilities.

Also known as: Google Lighthouse

Explained

Google Lighthouse is an automated, open-source performance auditing tool developed by Google’s Chrome team. It loads a webpage in a controlled Chrome environment and runs hundreds of tests across five categories: Performance, Accessibility, Best Practices, SEO, and Progressive Web App capabilities.

Each audit produces a score from 0–100 and provides specific, actionable recommendations. Lighthouse measures key metrics such as First Contentful Paint (FCP), Largest Contentful Paint (LCP), Total Blocking Time (TBT), and Cumulative Layout Shift (CLS). Because it aligns closely with Google’s Core Web Vitals, Lighthouse offers direct insight into how Google evaluates website quality and predicts future ranking signals.

Core Audit Categories

  • Performance: Measures Core Web Vitals and speed metrics such as LCP, FID, and CLS.
  • Accessibility: Evaluates screen-reader compatibility, color contrast, and keyboard navigation.
  • Best Practices: Checks HTTPS, modern APIs, browser compatibility, and security protocols.
  • SEO: Reviews meta tags, structured data, crawlability, and mobile optimization.
  • Progressive Web App: Assesses service workers, manifest files, and offline functionality.

Example

E-commerce brand Shopify increased their Lighthouse Performance score from 45 to 87, resulting in a 15% increase in checkout completion rates and $2.1M in additional annual revenue from improved organic search visibility.

Related terms

Core Web Vitals Largest Contentful Paint (LCP) First Contentful Paint (FCP) Time to First Byte (TTFB) Site Speed JavaScript SEO Lazy Loading