lighthouse

name	lighthouse
description	Run Lighthouse audits for performance, accessibility, and best practices scoring. Use when checking page performance, running quality audits, measuring Core Web Vitals, or getting a quantitative quality score for a web page.
compatibility	Requires Lighthouse CLI (npm i -g lighthouse)
metadata	{"author":"ridgeline","version":"1.0"}

Lighthouse Audit

Run Google Lighthouse for quantitative quality scores across performance, accessibility, and best practices.

Running an audit

npx lighthouse <url> --output json --output-path ./lighthouse-report.json --only-categories=performance,accessibility,best-practices --chrome-flags="--headless=new --no-sandbox"

For a quick text summary:

npx lighthouse <url> --output html --output-path ./lighthouse-report.html --only-categories=performance,accessibility,best-practices --chrome-flags="--headless=new --no-sandbox"

Reading results

Parse the JSON output to extract category scores:

node -e "
const r = require('./lighthouse-report.json');
const cats = r.categories;
console.log('Performance:', Math.round(cats.performance.score * 100));
console.log('Accessibility:', Math.round(cats.accessibility.score * 100));
console.log('Best Practices:', Math.round(cats['best-practices'].score * 100));
"

Score thresholds

• Performance > 90: Good
• Performance 50–90: Needs improvement
• Performance < 50: Poor
• Accessibility > 90: Good (aim for 100)
• Accessibility < 90: Needs attention

Severity mapping

• Accessibility score < 90 when design.md requires WCAG → blocking
• Performance or best practices concerns → suggestion
• All scores are informational by default — context determines severity

Gotchas

• Lighthouse scores vary between runs (±5 points). Run 3 times and take the median for reliable results.
• Local dev servers often score low on performance due to unminified assets. This is expected.
• Lighthouse requires a running page — start the dev server first.