# Lighthouse

> Google's open-source audit tool — scores performance, accessibility, best practices and SEO in a lab environment.

Lighthouse is the audit built into Chrome DevTools and PageSpeed Insights: it loads a page on a throttled simulated device and reports scores plus the specific opportunities behind them — unoptimized images, render-blocking scripts, missing alt attributes, bad contrast. The scores are a lab measurement, which makes them reproducible but not identical to what users experience — that is the field data CrUX collects and what the ranking systems actually consult.

The right reading: use the lab score as a regression test and diagnostics list, not as the goal. A 100 is achievable on a page that still feels slow on a real phone, and a 92 with clean field data is the better outcome. The opportunities list is the value — the number is just the summary.

## Related terms

- https://dfieldsolutions.com/en/glossary/core-web-vitals.md
- https://dfieldsolutions.com/en/glossary/lcp.md
- https://dfieldsolutions.com/en/glossary/inp.md
- https://dfieldsolutions.com/en/glossary/cls.md

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Source: https://dfieldsolutions.com/en/glossary/lighthouse
DField Solutions — Dunakeszi, Hungary — dezso@dfieldsolutions.com
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