Lighthouse in Chrome: mobile audit with DevTools or the extension

To run a Lighthouse mobile audit in Chrome, open DevTools, select the Lighthouse panel, set Device to Mobile, choose the categories you want (Performance, Accessibility, Best practices, SEO) and click Analyze page load. Lighthouse reloads the page on an emulated mid-range phone with a throttled connection and produces a report with scores from 0 to 100 and a list of issues to fix. Run it in an Incognito window, because other extensions can distort the results.

Lighthouse is also what Google recommended in place of its retired Mobile-Friendly Test; see Mobile-Friendly Test alternatives.

Step by step in Chrome DevTools

1. Open the page in an Incognito window (Ctrl + Shift + N or Cmd + Shift + N). Extensions do not run there by default.
2. Open DevTools (F12 or Cmd + Option + I) and select Lighthouse. If you do not see it, find it under the >> overflow arrow.
3. Choose the Mode:
   • Navigation (default): audits a fresh page load. Use this most of the time.
   • Timespan: records while you interact, useful for measuring a menu or a form.
   • Snapshot: audits the page in its current state, for example with a modal open.
4. Set Device to Mobile.
5. Select the Categories you need.
6. Click Analyze page load and wait about 30–60 seconds.

Lighthouse works on any page Chrome can open, including localhost and pages behind a login, which online tools cannot reach.

The Lighthouse Chrome extension

Lighthouse is also available as a Chrome extension from the Chrome Web Store: install it, open the page, click the Lighthouse icon and choose Generate report. Google’s own documentation recommends the DevTools panel unless you have a specific reason to use the extension, because DevTools can audit local sites and pages behind a login and the extension cannot. In practice, the extension is handy when you want a one-click audit of a public page without opening DevTools; for everything else, use the steps above.

Running Lighthouse from the command line

For repeatable runs or CI, use the Node CLI:

npx lighthouse https://example.com --view

The CLI audits as mobile by default. Add --preset=desktop for desktop, --only-categories=performance,seo to limit the categories, and --output=json to process results in a script. PageSpeed Insights runs the same engine on Google’s servers for public URLs.

Reading the report

Each category gets a score: 90–100 is good (green), 50–89 needs improvement (orange), 0–49 is poor (red).

Performance is based on lab metrics: First Contentful Paint, Largest Contentful Paint, Total Blocking Time, Cumulative Layout Shift and Speed Index. Under the score, Insights and Diagnostics list concrete fixes, such as oversized images, a late-discovered LCP image or render-blocking resources. Since Lighthouse 13 (October 2025), the older performance audits are grouped into these insights, the same ones shown in the DevTools Performance panel.

Accessibility runs automated checks: colour contrast, missing labels and alt text, heading order, viewport zoom settings and touch target size, among others.

Best practices covers HTTPS, browser errors in the console, deprecated APIs and image aspect ratios.

SEO checks the basics: a title and meta description, an indexable page with a successful status code, crawlable links with descriptive text, image alt text, a valid robots.txt, hreflang and canonical tags. Lighthouse 13 dropped the old legible font size audit and moved the viewport check into the performance insights. Passing these does not mean a page will rank; it means nothing basic is in the way.

Why mobile scores are lower and vary between runs

Mobile mode simulates a slower phone and network, so a page that scores 95 on desktop can score 60 on mobile. That gap is the point: it approximates the experience of many real visitors.

Scores also change from run to run, sometimes by 5–10 points, because of network conditions, server response time and background activity on your computer. To get a reliable figure:

• run the audit three to five times and use the median
• close other heavy tabs and apps
• compare like with like (same device setting, same page, same machine)

For speed, Lighthouse is a lab test. Real-user field data from PageSpeed Insights or Search Console is what reflects your visitors. The difference is explained in the mobile page speed test guide.

What to fix first

1. Anything red in Accessibility and SEO. These are usually quick fixes: labels, alt text, contrast, a missing meta description, a blocked crawler.
2. The largest LCP opportunity. Often a hero image that is too big, lazy-loaded, or discovered late.
3. Long JavaScript tasks. Third-party scripts are frequent offenders; see what you can defer or remove.
4. Layout shifts. Add dimensions to images, embeds and ad slots.

Lighthouse lists problems, but it does not show you what the page looks like on a phone. Pair it with a visual check in a mobile view: DevTools device mode, or a mobile view extension that reloads the page at a real phone size with a mobile user agent. Then work through the mobile website testing checklist for the things automated audits cannot judge, such as navigation and forms.

Frequently asked questions

How do I run Lighthouse for mobile in Chrome?

Open DevTools, go to the Lighthouse panel, set Device to Mobile, select categories and click Analyze page load. Use an Incognito window for cleaner results.

What is a good Lighthouse mobile score?

90 or above is rated good. For performance, focus on passing Core Web Vitals in real-user data; the lab score is a guide for finding problems.

Is Lighthouse the same as PageSpeed Insights?

PageSpeed Insights runs Lighthouse on Google’s servers and adds real-user data from the Chrome User Experience Report when it is available. Lighthouse in DevTools runs on your computer and can test local and private pages.