Performance
Lighthouse
Lighthouse is Google's open-source automated auditing tool for web pages. It produces a 0-100 score across performance, accessibility, best practices, SEO, and PWA, plus actionable recommendations.
In depth
Lighthouse runs against a single URL using Chrome under simulated mobile conditions (Slow 4G throttle, mid-tier CPU). It is the engine behind PageSpeed Insights, Chrome DevTools' Audits panel, and many CI integrations.
Key distinction: Lighthouse is **lab data** — synthetic, repeatable, but not necessarily representative of real users. Lab and field (CrUX) numbers can disagree significantly. Both matter: lab catches regressions in CI, field tells you what users actually experience.
Why it matters
Lighthouse is the de-facto standard for web performance auditing. Building a Lighthouse run into your CI prevents performance regressions before deploy, and tracking the score over time reveals whether your team is investing in performance or trading it away.
How Lemwatch helps with lighthouse
Lemwatch monitors lighthouse continuously and alerts you the moment something changes.
Lighthouse audits →Related terms
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LCP
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Page Speed
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Real User Monitoring
Real User Monitoring (RUM) captures actual page load performance in real visitors' browsers — LCP, INP, CLS, T…
CLS
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Browse the full Lemwatch monitoring glossary (47 terms).