Trial version. This site is still being built, so the list and the name may change. About

Tools

Tools for page speed and Core Web Vitals

Speed can be measured in two ways. A lab test loads a page once, in a controlled setup, and reports what happened. Field data is collected from real visitors over weeks. The two often disagree, and that is expected rather than a fault.

For Core Web Vitals and Page speed, a lab test helps find the cause of a slow load, and field data shows whether visitors met it. Tools that show how the browser builds and paints a page also bear on Rendering.

PageSpeed Insights puts both kinds of data side by side for one page, which makes it an easy place to begin.

Free tools

PageSpeed Insights

GoogleFree

Reports on a page's user experience for mobile and desktop. It shows field data from the Chrome UX Report and lab data from Lighthouse, with suggestions for improvement. Core Web Vitals results are shown as pass or fail for the page or the whole site.

Field data appears only where enough real visitors have been recorded. Otherwise the report may fall back to whole-site data or show none.
Lighthouse in Chrome DevTools

GoogleFree

An open-source auditing tool with a panel in Chrome DevTools. It audits performance, accessibility, SEO and more, and each failed audit explains why it matters and how to fix it. It can also run from the command line, and it can test pages that need a login.

It gives lab data only, from one test on one device setup. A good lab result does not guarantee a good experience for real visitors.
Chrome UX Report (CrUX)

GoogleFree

A Google dataset of how real Chrome users experience websites, including the Core Web Vitals. It can be viewed through several Google tools and third-party tools.

It covers only sites and pages that are public and have enough visitors, and only users whose Chrome settings allow it.
WebPageTest

Catchpoint (part of LogicMonitor)Free with limits

A testing service that loads a page in a real browser from a chosen test location and reports how it loaded, step by step, including a filmstrip of the page as it appears and Lighthouse results.

The free plan needs an account and has a monthly allowance of test runs. Paid plans add more runs and features.

How to choose

Begin with PageSpeed Insights on a page you care about. Look at the field data first if it is there, then at the lab results for causes.

Lighthouse suits testing while you build, and pages behind a login. WebPageTest gives a slower, closer look at how a single page loads. A learner can get a long way with these free tools, so paid ones are left off this page.