Our verdict on Lighthouse

Lighthouse is the first tool to open when you want to check the speed and SEO basics of an adult page, including one behind an age gate, because DevTools keeps your browser cookies. It is free, already in Chrome, and its scores are the ones PageSpeed Insights shows.

It audits one page at a time and does not crawl a site.

Lighthouse

How the Lighthouse performance score is calculated

The performance score is a weighted average of five metrics: Total Blocking Time 30%, Largest Contentful Paint 25%, Cumulative Layout Shift 25%, First Contentful Paint 10% and Speed Index 10%. 90 to 100 is good, 50 to 89 needs improvement, and 0 to 49 is poor. Scores move between runs depending on hardware and network, so compare several runs before acting on one number.

Running Lighthouse behind an age gate

The Lighthouse panel in DevTools never clears your cookies. Click through the age gate in Chrome, then audit the page. From the CLI, --extra-headers can send a Cookie header, though it overrides any other cookies. The Chrome extension cannot test authenticated pages, so use DevTools.

Google's guidance for explicit content asks you to let a verified Googlebot crawl without triggering the age gate. Lighthouse does not check that setup, nor the rating meta tag that marks a page as explicit.

What the SEO category checks

Indexability, title and meta description.
HTTP status code, descriptive and crawlable links.
A valid robots.txt and image alt text.
Correct hreflang and canonical tags.

Structured data stays a manual check. Since version 13.3 in May 2026, an agentic browsing category also scores how well AI agents can read and use the page.

Ways to run Lighthouse

Google recommends the Lighthouse tab in Chrome DevTools. The CLI and Node module need Chrome and Node 22.19 or later, and Lighthouse CI runs audits on every build. For a public page with nothing to install, PageSpeed Insights runs Lighthouse for you.

Lighthouse strengths and limitations

Strengths

Free and open source, already in Chrome.
Keeps cookies in DevTools, age gates included.
CI-friendly for every deploy.

Limitations

One page per run, no site crawl.
Scores vary between runs.
No check of the adult rating tag.

Lighthouse and related tools

PageSpeed Insights adds real Chrome user data to Lighthouse scores, for public pages only. To audit a whole site, Sitebulb Desktop or SiteOne Crawler crawl every page.