How to read your own Lighthouse report

The scores are a signal, not a grade

Open Chrome DevTools, run Lighthouse, and you get four numbers from 0 to 100: Performance, Accessibility, Best Practices, SEO. They are useful as a temperature reading and misleading as a target. Chasing a perfect 100 burns hours on warnings that change nothing a visitor will ever feel. The scores are where you start looking, not what you fix.

Here is how to read past them.

Performance is the hard one, and the one that matters

The Performance score is a blend of timing metrics, and two of them carry most of the weight. Largest Contentful Paint is how long until the biggest thing on screen renders; good is under 2.5 seconds. Cumulative Layout Shift measures how much the page jumps around as it loads; good is under 0.1. If you only watch two numbers, watch those. A site can score 100 on the other three categories and still feel broken if LCP sits at five seconds.

One caveat: the lab score from your laptop is run on a simulated mid-range phone, but your laptop is not throttled the way a real network is. Treat the lab number as directional and confirm against field data when you have it.

Accessibility, SEO, and Best Practices are mostly checklists

These three are far more pass/fail, which makes them the faster wins. The SEO check confirms the unglamorous mechanics: a title, a meta description, a crawlable page, valid links. Accessibility checks contrast, alt text, form labels, and landmarks. Best Practices flags things like missing HTTPS or console errors. Most items here are a yes or a no, and most are quick to correct once you know they exist.

The list below the score is the actual report

Scroll past the gauges. The Opportunities and Diagnostics sections are where Lighthouse tells you exactly what is costing you time and points, usually with an estimate of how much each fix saves. That list is the report. The number at the top is just its average.

What to fix first

Resist fixing top to bottom. Find the single largest contributor to LCP, which is often one render-blocking stylesheet, one oversized hero image, or a late-loading font, and fix that before anything else. It will move the number more than the next ten warnings combined. An audit without that prioritization is just a longer to-do list.

Always run it on mobile

Run the report in mobile mode, throttled. That is the version Google uses to rank you, and it is where the gaps are widest. A site that scores well on desktop and poorly on mobile is a site optimized for the wrong visitor.

Would rather not read the report yourself? Get a free audit. Same checks, ranked by impact, emailed to you as a report. No call required.