Lighthouse
A built-in DevTools audit that scores a page on speed, accessibility, and best practices, then lists what to fix.
Performance
- Load speed
- Image sizes
- Blocking scripts
Accessibility
- Contrast
- Labels
- Keyboard use
SEO & best practices
- Titles
- Security
- Console errors
What it is
Lighthouse is a tab in Chrome DevTools that loads your page like a visitor on a typical phone and grades it out of 100 in four areas: Performance, Accessibility, Best Practices, and SEO.
Under each score is a list of specific problems: images that are too large, text with poor contrast, buttons without labels. Each item names the element involved.
The scores move around a bit between runs, so treat them as a guide. The list of issues is the useful part, and it's easy to hand straight to an agent.
How to ask for it
“Make the site faster.”
“Lighthouse gives the home page Performance 54 on mobile. The top issues are a 2.4 MB hero image and render-blocking fonts. Fix those two, then rerun Lighthouse and tell me the new score.”
Lighthouse turns "faster" into named issues and a measurable before-and-after.
You've seen this in
- CThe Lighthouse tab in Chrome DevTools
- GGoogle's PageSpeed Insights website
- GGreen, orange, and red score circles