PageSpeed Insights is free and useful, so the question is less “what replaces it” than “what does it not show”. It tests one URL at a time, combines real-user data from the Chrome UX Report with a Lighthouse lab test on a simulated phone, and lists opportunities. Its gaps are site-wide coverage, test conditions you can control, and detail on why a page is slow.
What PageSpeed Insights does well
- Field data: Core Web Vitals (LCP, INP, CLS) from real Chrome users over the last 28 days, at the 75th percentile, for the page and for the whole origin, when there is enough traffic.
- Lab data: a Lighthouse run with a list of opportunities and diagnostics.
- It is free and needs no account. There is also an API.
Its gaps, and what fills each one
| You need | Use |
|---|---|
| A test while developing, before the page is public | Lighthouse in Chrome DevTools |
| Exactly what loads and in which order (waterfall, filmstrip, test location and connection) | WebPageTest |
| The main-thread work behind a slow interaction | Chrome DevTools → Performance panel |
| Real-user trends over months | The CrUX History API or a CrUX dashboard |
| Every page type of a site, not one URL | A site-wide audit |
| Your own real-user data, including browsers other than Chrome | Real-user monitoring in your analytics or a RUM service |
Why lab scores differ between tools
Lighthouse simulates a slow phone, and the result depends on the machine running the test. The same page can score differently in PageSpeed Insights, in your DevTools and in another tool, and from one run to the next. Compare metrics such as LCP and TBT on the same tool over time rather than chasing a single score, and trust field data for what visitors actually experience.
A site-wide view
Speed problems usually belong to a template: if one product page is slow, they all are. SignalCrawler runs Lighthouse on representative pages of each template, adds real-user Core Web Vitals from the Chrome UX Report where Google has data, and turns the common causes into tasks: unused JavaScript and CSS, heavy images and legacy formats, render-blocking files, short cache times, third-party scripts and a lazy-loaded main image. Each task lists the pages and templates it affects.
For a single page's loading details, WebPageTest and Chrome DevTools remain the better tools.