Page Speed & Core Web Vitals
Google Lighthouse: what it does, what it costs
The audit engine behind everyone's page speed score — free, open source, and scriptable.
Google Lighthouse at a glance
Every row is a verified field or an honest absence. A row is dropped rather than filled with an em dash, so the length of this table says how complete the record is.
| What it is | The audit engine behind everyone's page speed score — free, open source, and scriptable. |
|---|---|
| Category | Page Speed & Core Web Vitals |
| Best suited for | Developers and technical SEOs who want the engine rather than a dashboard |
| Starting price | Free and open source |
| Free plan | Yes |
| Free trial | None offered |
| Main strength | Free and open source, with no quota, key or rate limit |
| Main limitation | Lab data only — it simulates one visit and tells you nothing about real users |
| Evidence | Primary-source researched |
| Closest alternatives | PageSpeed Insights, Google Search Console, Sitebulb |
| Pricing checked | 20 August 2026 |
| Record checked | 20 August 2026 |
What Google Lighthouse is
Lighthouse is the engine, not a product. When a tool shows you a performance score out of 100, it is usually Lighthouse underneath — including PageSpeed Insights. Understanding that changes how you use it: rather than reading someone's dashboard, you can run the same audits yourself, on any URL, against any environment.
Its real advantage over the hosted tools is reach. Lighthouse can audit pages that require authentication, and pages that are not public at all — localhost, a staging site, a build in CI. That covers exactly the cases where you most want to catch a problem, which is before the page ships. It runs in Chrome DevTools, from the command line after `npm install -g lighthouse`, or as a Node module you call programmatically, and a report takes 30 to 60 seconds.
The piece most people miss is Lighthouse CI, which runs the audits on every commit and fails the build when scores regress. That turns performance from something you measure after a complaint into something that cannot silently get worse — which is a different kind of tool from anything else in this category. Reports export as JSON or share as GitHub gists, and stack packs give framework-specific advice.
What you can use it for
- Audit performance, accessibility, SEO and best practices on any page
- Test pages behind a login, on localhost or on a staging build
- Fail a CI build when performance scores regress, using Lighthouse CI
- Script audits across many URLs from the command line or Node
- See the same engine's output that PageSpeed Insights reports
The features that matter for SEO
Each one says what it does and the SEO job it serves. A vendor feature list without that second half tells you nothing you could not read on their own site.
Audits authenticated and non-public pages
Runs against any URL you can reach, including pages behind a login, on localhost or on staging.
The decisive difference from PageSpeed Insights, which can only fetch public URLs. Logged-in templates and pre-release builds are where problems are cheapest to fix.
Four audit categories
Scores performance, accessibility, SEO and best practices, each audit with a reference explaining why it matters and how to fix it.
The explanations are the underrated part — they make the report usable by a developer who does not do SEO, which is usually who has to act on it.
The SEO category is a basic crawlability and markup check, not a substitute for an SEO audit.
Lighthouse CI
Runs audits in continuous integration and can fail a build on regression.
Converts performance from a periodic measurement into a standing gate. This is the only tool in the category that can stop a regression from shipping rather than reporting it afterwards.
Command line and Node module
Installs via npm and runs as a CLI or programmatically.
Makes bulk auditing trivial — a shell loop over a URL list costs nothing and hits no quota, unlike the hosted APIs.
JSON output and shareable reports
Exports reports as JSON and can publish them as GitHub gists for viewing.
JSON is what lets you track scores over time in your own store rather than re-running audits to compare.
Stack packs
Adds framework-specific guidance for the platform a page is built on.
Turns generic advice into instructions that match the codebase, which is the difference between a report being actioned and being filed.
Plugins
Allows custom audits to be added to the run.
Lets a team encode its own standards as pass or fail checks alongside Google's.
Pricing and limits
Starting price: Free and open source Checked 20 August 2026 Vendor’s own pricing page
| Plan | Price | What it includes |
|---|---|---|
| Free | Free | Free in the way an open-source tool is free. The constraint is your own hardware, which is also why results vary between machines.
|
Strengths and limitations
Strengths
- Free and open source, with no quota, key or rate limit
- Audits authenticated, local and staging pages that hosted tools cannot reach
- Lighthouse CI can block a regression before it ships
- Scriptable from the CLI or as a Node module
- Every audit comes with an explanation of why it matters and how to fix it
Limitations
- Lab data only — it simulates one visit and tells you nothing about real users
- Scores vary with your machine, network and even browser extensions
- Requires Chrome and, for the CLI, Node
- The SEO category is a shallow check, not an SEO audit
- No history, no dashboard and no reporting layer of its own
Who it is for, and who should skip it
Worth it if
- Developers and technical SEOs who want the engine rather than a dashboard
- Auditing pages that are behind a login or not yet public
- Preventing performance regressions in CI
Skip it if
- You want field data from real users rather than a lab simulation
- You want a hosted report with no setup
- You need tracked history without building it yourself
Alternatives to Google Lighthouse
Each one answers when it is the better choice, which is the only thing a list of competitors is useful for.
- PageSpeed Insights Choose it when you want this same engine hosted, plus real-user CrUX field data, with nothing to install.
- Google Search Console Choose it when you want Core Web Vitals for your whole site as Google actually measured it.
- Sitebulb Choose it when you want performance findings inside a full site crawl with prioritised explanations.
Sources and verification
Last verified 20 August 2026 0 days ago
Pricing 20 August 2026 Plans 20 August 2026 Features 20 August 2026
- Introduction to Lighthouse Documentation verifies features, pricing, plans checked 20 August 2026
What changed
- 20 August 2026 — Carried as SEO-first on the same basis as PageSpeed Insights and Search Console — it ships a dedicated SEO audit category and is the measurement layer behind Core Web Vitals work, even though it is a general web-quality tool rather than an SEO product.
- 20 August 2026 — Listed separately from PageSpeed Insights despite sharing an engine. They differ in what they can reach and what data they return — Lighthouse runs locally on any page and gives lab data only, PSI is hosted, public-URL-only and adds real-user field data. Choosing between them is a real decision, so both are listed.
Questions
What is the difference between Lighthouse and PageSpeed Insights?
PageSpeed Insights runs Lighthouse for you and adds real-user field data from the Chrome UX Report, but it can only fetch public URLs. Lighthouse runs on your machine, so it can audit pages behind a login, on localhost or in CI — but it only ever gives you lab data from that one simulated visit.
Is Lighthouse free?
Yes, and open source. There is no account, key, quota or rate limit, because it runs on your own hardware. That is also why two people can audit the same page and get different scores.
What is Lighthouse CI for?
Running the audits on every commit and failing the build when scores drop. It is the only thing in this category that prevents a performance regression rather than reporting one after users have already met it.