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PageSpeed Insights vs Lighthouse vs CrUX: Three Views of One Site
These are not three competing tools. CrUX is the data, Lighthouse is the simulator, and PageSpeed Insights is the page that shows you both.
Запусти свіжий аудит DomainLens і використовуй звіт як список пріоритетів.
How they relate
CrUX — the Chrome User Experience Report — is a dataset of real-user measurements collected from Chrome users who opted in. It is the source of every field number you see anywhere, including in Search Console.
Lighthouse is an auditing tool that loads a page in a controlled environment and measures it. PageSpeed Insights is a web interface that shows CrUX field data at the top and runs Lighthouse underneath. Understanding that removes most of the confusion about why the numbers differ.
| CrUX | Lighthouse | PageSpeed Insights | |
|---|---|---|---|
| What it is | A dataset | An auditing tool | An interface over both |
| Data type | Field | Lab | Both |
| Access | API, BigQuery, dashboards | CLI, DevTools, CI | A web page |
| Granularity | URL and origin | A single load | URL, with origin fallback |
| Used for ranking | Yes | No | Its CrUX half |
When to use each
The CrUX API is the underused one. It answers "are real users having a bad time on these fifty URLs" in seconds, without a single page load.
- PageSpeed Insights — a quick look at one URL, with both views side by side. The default choice.
- Lighthouse in DevTools — deep diagnosis with a trace, on a page you can interact with and re-run cheaply.
- Lighthouse CI — catching regressions before deploy, where consistency matters more than realism.
- CrUX API — building your own monitoring, or checking many URLs without running a browser.
- CrUX in BigQuery — analysing at scale, including competitor origins over time.
Why field data is sometimes missing
CrUX needs enough Chrome samples to report without identifying anyone. A URL below that threshold gets nothing, and PageSpeed Insights falls back to origin-level data covering your whole site rather than that page.
That fallback is easy to misread. Seeing decent numbers on a new page often means you are looking at the origin average, not the page — and the page could be far worse.
The 28-day window and what it hides
CrUX reports a rolling 28-day aggregate at the 75th percentile. Two consequences follow. A fix deployed today is diluted by 27 days of the old experience, so improvement appears gradually rather than at once. And the 75th percentile means a quarter of your users had a worse experience than the number shown — passing is not the same as everyone being fine. See Core Web Vitals vs Lighthouse score for the scoring question and what LCP measures for the metric itself.
How DomainLens contributes
DomainLens pulls CrUX field data and Lighthouse lab results together with the rest of the audit, so performance sits beside indexability and on-page findings rather than in a separate tab. When field data is absent it says so rather than quietly substituting origin numbers. See the Core Web Vitals guide .
- Is PageSpeed Insights the same as Lighthouse?
- No. PageSpeed Insights runs Lighthouse for its lab section and shows CrUX field data above it. Lighthouse is the tool; PSI is the interface presenting both.
- What is CrUX?
- The Chrome User Experience Report — real-user performance data from opted-in Chrome users. It is the source of every field metric, including the ones in Search Console.
- Why does PageSpeed Insights show no field data?
- Not enough Chrome samples for that URL. It then falls back to origin-level data, which describes your whole site rather than the page you tested.
- Which should I use for monitoring?
- The CrUX API for field data across many URLs, and Lighthouse CI to catch regressions before deploy. PageSpeed Insights is for one-off investigation.