Lighthouse analyzes web apps and web pages, collecting modern performance metrics and insights on developer best practices.
Using Lighthouse in Chrome DevTools
Lighthouse is integrated directly into the Chrome Developer Tools, under the "Audits" panel.
Installation: install Chrome.
Run it: open Chrome DevTools, select the Audits panel, and hit "Perform an Audit...".
Using the Chrome extension
Installation: install the extension from the Chrome Web Store.
Run it: follow the extension quick-start guide.
Using the Node CLI
Lighthouse requires Node 6 or later.
npm install -g lighthouse # or use yarn: # yarn global add lighthouse
By default, Lighthouse writes the report to an HTML file. You can control the output format by passing flags.
$ lighthouse --help lighthouse <url> Logging: --verbose Displays verbose logging [boolean] --quiet Displays no progress, debug logs or errors [boolean] Configuration: --save-assets Save the trace contents & screenshots to disk [boolean] --save-artifacts Save all gathered artifacts to disk [boolean] --list-all-audits Prints a list of all available audits and exits [boolean] --list-trace-categories Prints a list of all required trace categories and exits [boolean] --additional-trace-categories Additional categories to capture with the trace (comma-delimited). --config-path The path to the config JSON. --chrome-flags Custom flags to pass to Chrome (space-delimited). For a full list of flags, see http://peter.sh/experiments/chromium-command-line-switches/. Environment variables: CHROME_PATH: Explicit path of intended Chrome binary. If set must point to an executable of a build of Chromium version 54.0 or later. By default, any detected Chrome Canary or Chrome (stable) will be launched. [default: ""] --perf Use a performance-test-only configuration [boolean] --port The port to use for the debugging protocol. Use 0 for a random port [default: 9222] --hostname The hostname to use for the debugging protocol. [default: localhost] --max-wait-for-load The timeout (in milliseconds) to wait before the page is considered done loading and the run should continue. WARNING: Very high values can lead to large traces and instability [default: 25000] Output: --output Reporter for the results, supports multiple values [choices: "json", "html", "domhtml"] [default: "html"] --output-path The file path to output the results. Use 'stdout' to write to stdout. If using JSON output, default is stdout. If using HTML output, default is a file in the working directory with a name based on the test URL and date. If using multiple outputs, --output-path is ignored. Example: --output-path=./lighthouse-results.html --view Open HTML report in your browser [boolean] Options: --help Show help [boolean] --version Show version number [boolean] --blocked-url-patterns Block any network requests to the specified URL patterns [array] --disable-storage-reset Disable clearing the browser cache and other storage APIs before a run [boolean] --disable-device-emulation Disable Nexus 5X emulation [boolean] --disable-cpu-throttling Disable CPU throttling [boolean] [default: false] --disable-network-throttling Disable network throttling [boolean] Examples: lighthouse <url> --view Opens the HTML report in a browser after the run completes lighthouse <url> --config-path=./myconfig.js Runs Lighthouse with your own configuration: custom audits, report generation, etc. lighthouse <url> --output=json --output-path=./report.json --save-assets Save trace, screenshots, and named JSON report. lighthouse <url> --disable-device-emulation --disable-network-throttling Disable device emulation lighthouse <url> --chrome-flags="--window-size=412,732" Launch Chrome with a specific window size lighthouse <url> --quiet --chrome-flags="--headless" Launch Headless Chrome, turn off logging For more information on Lighthouse, see https://developers.google.com/web/tools/lighthouse/.
lighthouse --output json generates
- json output on
lighthouse --output html --output-path ./report.html generates
NOTE: specifying an output path with multiple formats ignores your specified extension for ALL formats
lighthouse --output json --output html --output-path ./myfile.json generates
lighthouse --output json --output html generates
lighthouse --output-path=~/mydir/foo.out --save-assets generates
lighthouse --output-path=./report.json --output json --save-artifacts generates
lighthouse --save-artifacts generates
Viewing a report
Lighthouse can produce a report as JSON or HTML.
Running Lighthouse with the
--output=json flag generates a json dump of the run.
You can view this report online by visiting
In the Viewer, reports can be shared by clicking the share icon in the top right corner and signing in to GitHub.
Note: shared reports are stashed as a secret Gist in GitHub, under your account.
Docs & Recipes
Useful documentation, examples, and recipes to get you started.
- Using Lighthouse programmatically
- Testing a site with authentication
- Testing on a mobile device
- Lighthouse Architecture
The session from Google I/O 2017 covers architecture, writing custom audits, Github/Travis/CI integration, headless Chrome, and more:
click to watch the video
Read on for the basics of hacking on Lighthouse. Also see Contributing for detailed information.
# yarn should be installed first git clone https://github.com/GoogleChrome/lighthouse cd lighthouse yarn yarn install-all yarn build-all # The CLI is authored in TypeScript and requires compilation. # If you need to make changes to the CLI, run the TS compiler in watch mode: # cd lighthouse-cli && yarn dev
node lighthouse-cli http://example.com
Getting started tip:
node --inspect --debug-brk lighthouse-cli http://example.comto open up Chrome DevTools and step through the entire app. See Debugging Node.js with Chrome DevTools for more info.
# lint and test all files yarn test # watch for file changes and run tests # Requires http://entrproject.org : brew install entr yarn watch ## run linting, unit, and smoke tests separately yarn lint yarn unit yarn smoke ## run closure compiler (on whitelisted files) yarn closure ## import your report renderer into devtools-frontend and run devtools closure compiler yarn compile-devtools
This section details projects that have integrated Lighthouse. If you're working on a cool project integrating Lighthouse and would like to be featured here, file an issue to this repo or tweet at us @_lighthouse
Calibre - Calibre is a web performance monitoring tool running Lighthouse continuously or on-demand via an API. Test using emulated devices and connection speeds from a number of geographical locations. Set budgets and improve performance with actionable guidelines. Note that Calibre is a paid product with a free 14-day trial.
Treo - Treo is Lighthouse as a Service. It provides regression testing, geographical regions, custom networks, and integrations with Github & Slack. Treo is a paid product with plans for solo-developers and teams.
Web Page Test — An open source tool for measuring and analyzing the performance of web pages on real devices. Users can choose to produce a Lighthouse report alongside the analysis of WebPageTest results.
- webpack-lighthouse-plugin - run Lighthouse from a Webpack build.
- lighthouse-mocha-example - gather performance metrics via Lighthouse and tests them in Mocha
- pwmetrics - gather performance metrics
- lighthouse-hue - set the color of Philips Hue lights based on a Lighthouse score
- lighthouse-batch - run Lighthouse over a number of sites and generate a summary of their metrics/scores.
- lighthouse-cron - Cron multiple batch Lighthouse audits and emit results for sending to remote server.
- lightcrawler - Crawl a website and run each page found through Lighthouse.
How does Lighthouse work?
Can I configure the lighthouse run?
Yes! Details in Lighthouse configuration.
How does Lighthouse use network throttling, and how can I make it better?
Good question. Network and CPU throttling are applied by default in a Lighthouse run. The network
attempts to emulate 3G and the CPU is slowed down 4x from your machine's default speed. If you
prefer to run Lighthouse without throttling, you'll have to use the CLI and disable it with the
--disable-* flags mentioned above.
Read more in our guide to network throttling.
Are results sent to a remote server?
Nope. Lighthouse runs locally, auditing a page using a local version of the Chrome browser installed the machine. Report results are never processed or beaconed to a remote server.
How do I author custom audits to extend Lighthouse?
Tip: see Lighthouse Architecture for more information on terminology and architecture.
Lighthouse can be extended to run custom audits and gatherers that you author. This is great if you're already tracking performance metrics in your site and want to surface those metrics within a Lighthouse report.
If you're interested in running your own custom audits, check out our Custom Audit Example over in recipes.
How do I contribute?
We'd love help writing audits, fixing bugs, and making the tool more useful! See Contributing to get started.
Lighthouse, ˈlītˌhous (n): a
tower or other structure tool containing a beacon light
to warn or guide ships at sea developers.