Is a Lighthouse score of 100 required?

No. Aim for 90+ on Performance and SEO; 100 is nice but rarely worth the last 10 points of engineering.

Why does my score change every run?

Lighthouse simulates a slow network and CPU. Small variance is normal — trust the median of 3-5 runs, not a single number.

Does Lighthouse match what Google ranks on?

Not directly. Google ranks on field data (CrUX). Lighthouse is a lab simulation useful for debugging.

Does the Accessibility score cover everything?

No — it catches automatable issues (about 30% of WCAG). You still need manual review for a real accessibility audit.

Orbit·by Innovide

Article

Google Lighthouse Score Explained

GAP Team · Jul 16, 2026 · 7 min read

Lighthouse is Google's open-source auditing tool. It gives you four scores — Performance, Accessibility, Best Practices, SEO — and a giant list of opportunities. Here's how to actually use it.

How the Performance score is calculated

Weighted from lab metrics: LCP (25%), TBT (30%), CLS (25%), FCP (10%), SI (10%). Move the heaviest ones first. See what are Core Web Vitals.

What each category actually measures

Performance — simulated load speed and interactivity.
Accessibility — automatable a11y checks (contrast, labels, aria).
Best Practices — security, console errors, deprecated APIs.
SEO — basic on-page and crawlability checks.

How to improve your score

Fix the top three "Opportunities" first — they're sorted by potential impact. Then work through "Diagnostics". Full playbook: how to improve website speed.

Lighthouse vs. real users

Lighthouse throttles to a slow 4G / mid-tier CPU. Real users are usually faster — but Google ranks on the field. Compare both.

Frequently asked questions

Run Free GAP Scan