Lighthouse is Google's open source tool for auditing a web page. Site health runs it for you on the pages you track, on the device you picked for each page (mobile or desktop).
Open Site health and pick the Lighthouse tab
Select a page (or click Add in the header to add one first)
Click Run audit (Re-run audit once it has one)
An audit costs 1 credit and takes about a minute. Running audits needs Starter or higher; owners and editors can run them.
Score | What it measures |
|---|---|
Performance | Page load speed |
Accessibility | Usability for all, screen readers and keyboards included |
Best practices | Modern standards: HTTPS, no console errors, safe libraries |
SEO | Search optimization: title, description, crawlable links, mobile friendliness |
90 to 100 is good, 50 to 89 needs improvement, below 50 is poor.
Measured in the simulated run:
Metric | Good |
|---|---|
Largest Contentful Paint (main content visible) | 2.5 s or less |
First Contentful Paint (first content painted) | 1.8 s or less |
Total Blocking Time (delay before the page responds) | 200 ms or less |
Cumulative Layout Shift (how much the layout jumps) | 0.1 or less |
Time to First Byte (server response) | 800 ms or less |
Below the lab metrics, Real-user data (CrUX) shows how real Chrome users experienced the page over the last 28 days, at the 75th percentile. This is what Google uses for ranking. A page with little traffic shows the whole domain's figures instead, or no data yet.
The issues list shows what to fix, with its impact (High, Medium, Low). Filter by impact, and open an issue for the details. After a new audit, each issue is marked New, Worse, Still failing or Resolved now, and the list says how many issues were fixed since the previous audit.
Common fixes:
Performance: compress and resize images, defer scripts that are not needed right away, use a CDN
Accessibility: add alt text, raise color contrast, label form fields
Best practices: serve everything over HTTPS, fix JavaScript errors, update old libraries
SEO: write a meta description, keep titles about 50 to 60 characters, use normal links
Audit history lists earlier runs of the page with their scores. Open one to see it in full and Back to latest to return. Owners and editors can Delete audit. The score chart shows the trend across runs.
Scores move a few points between runs because of network and server timing. Look at the trend, not one run.
The page shows why and what to try. The usual causes: the page is not public, a firewall blocks audit tools, or it timed out. Check the page opens in a private window, then run it again. If Lighthouse cannot run, Technical audit checks what it can.
Email [email protected] and I'll help.
