Lighthouse scores that actually matter (and the ones that don't)
Lighthouse grades four categories. Two of them affect Google rankings directly. One affects conversion. One is mostly for developers. Here's how to prioritize.
Lighthouse gives you four scores — Performance, Accessibility, Best Practices, SEO. They all look important. They're not all equally important.
Performance (critical)
Google uses Core Web Vitals as a direct ranking factor. That means a slow site literally ranks lower than a fast one, all else equal. It also affects conversion directly — Amazon famously calculated that 100ms of extra load time cost them 1% in sales.
Target: 90+. Below 80, you're actively losing rankings and conversions.
SEO (critical)
Structured data, meta tags, alt text, canonical URLs, mobile-friendliness. This is a checklist Google uses to understand your site. Missing items mean Google is guessing — and Google doesn't rank what it doesn't understand.
Target: 95+. This is mostly binary — you have the tags or you don't.
Accessibility (important)
Accessibility is about whether your site works for everyone — screen readers, keyboard users, high-contrast preferences. Legally, US sites need to meet WCAG 2.1 AA in many contexts. Ethically, it's the right call. Commercially, accessibility problems overlap 90% with UX problems that also hurt conversion.
Target: 95+. Low-hanging fruit: alt text on images, semantic HTML, proper form labels, color contrast.
Best Practices (nice to have)
This is the developer-facing category. HTTPS, no deprecated APIs, no console errors, proper aspect ratios on images. It matters for code quality but doesn't directly affect rankings or conversion.
Target: 85+. Below that, you likely have bugs causing other problems.
The order of operations
- Fix Performance first — biggest direct impact on rankings + conversion.
- Then SEO — quick wins, mostly structured data + meta tags.
- Then Accessibility — also mostly quick fixes, reduces legal exposure.
- Best Practices last — diminishing returns past 85.
Our free website audit runs all four categories and prioritizes issues by impact. Most sites we audit land in the 50–70 range on Performance, which means immediate easy wins.
