What does Lighthouse do?

Lighthouse is a tool from Google that automatically analyzes a web page and produces a performance and quality score across several categories.

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#What it checks:

1. Performance

• LCP, FCP, TTI, TBT, CLS
• loading speed, interactivity, layout stability

2. Accessibility

• text contrast, alt tags, keyboard access, aria attributes

3. Best Practices

• HTTPS, secure requests, banning unsafe APIs

4. SEO

• presence of a title tag, meta description, correct indexing, semantics

5. PWA (Progressive Web App)

• offline mode, manifest, service worker

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#How it works:

• Loads the page like a regular user
• Measures key metrics (including Web Vitals)
• Checks the DOM, CSS, JS structure, and accessibility
• Generates a detailed report with scores and advice

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#Where to use it:

• The Lighthouse tab in Chrome DevTools
• Via the CLI (lighthouse https://site.com)
• Via CI (Lighthouse CI)
• Via API integrations or third-party tools (for example, PageSpeed Insights uses Lighthouse internally)

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Conclusion: Lighthouse is an automated site audit for performance, accessibility, SEO, and stability. It provides metrics, a report, and recommendations to help you understand what slows the site down and how to fix it.