30,842 stars · Apache-2.0, read from /blob/main/LICENSE — plain and unmodified, but the appendix is left as the template 'Copyright [yyyy] [name of copyright owner]'; the real notice lives in source headers as 'Copyright 2016 Google LLC' · v13.5.0 (2026-09-18), read from /releases/latest as a yearless '18 Sep 16:18' and settled by the ungh releases record (2026-09-18T16:18:20Z); package.json agrees on 13.5.0 · Track this in Scout
Loads one web page in a real browser, runs about a hundred checks, and prints a scored report on speed, accessibility and search readiness.
▶Repo detailsthe review · specs · pros & cons · install
What it is
Lighthouse is a program written by the team that makes the Chrome browser. It opens a page the way a visitor would, measures how long each part takes to appear, and then reports five scores: speed, accessibility, best practice, search readiness, and progressive web app.
What it is good for. Anyone who publishes a web page and has never been told what is wrong with it. It is the same measuring engine that sits behind the Chrome developer tools and behind Google's own PageSpeed Insights website, so the numbers agree with the numbers other people will quote back. It is most useful in two situations: a site that feels slow and nobody can say why, and a page that is not appearing in search results.
- It is free, and it is written by the people who make the browser that most visitors use.
- It only reads. It visits the page, measures, prints, and stops. Nothing on the page is altered.
- The report explains each failure in words, with a link to a page describing the fix.
- It needs Node.js (a way to run JavaScript programs outside a browser) version 22 or later, and a real Chrome or Chromium browser version 66 or later installed on the machine. Neither is heavy, but both have to be there.
- The project publishes no memory, disk or processor figure anywhere. It drives a whole browser, so a small machine running other work will feel it.
- The licence file leaves the copyright holder as the unfilled template,
Copyright [yyyy] [name of copyright owner]. The real notice lives in the source files, which say "Copyright 2016 Google LLC". The terms themselves are plain Apache-2.0, which is permissive and carries no commercial restriction.
sitespeedio/sitespeed.ioMeasures the same page-speed numbers from a real browser, but it is built to run on a schedule and keep the history, where Lighthouse is one report at one moment.
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harlan-zw/unlighthouseIt runs Lighthouse itself, and crawls a whole site so every page is scored in one sweep rather than one address at a time.
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Tests a page from many real locations and devices, where Lighthouse runs locally on one machine; its last code landed on 19 September 2025.
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npm install -g lighthouse lighthouse https://example.com --view
