WebPageTest
webpagetest.org
Loads your page from a chosen city and browser and films the result
No sign-upClassic
Loading page
pagespeed.web.dev
Scores a page on real-user Core Web Vitals and lab measurements.
Google's front end to Lighthouse, and the only public tool that shows both a lab run and the field data from actual Chrome users on that URL. The two often disagree, and the field numbers are the ones affecting search. The report ranks opportunities by estimated saving, which is the part worth acting on. Field data only appears for pages with enough real traffic, and lab scores swing several points between runs on identical code.
AltFTool does this too
If you would rather not leave the site, Web Speed Checker covers the same job here — free, no account, and it runs in your browser.
Open Web Speed CheckerQuestions
Works the moment the page loads. No account, no email, no trial. Field data is missing for low-traffic pages, and repeat lab runs vary by several points on unchanged code.
Yes. PageSpeed Insights sends your input to its own servers to process it. That is fine for public material; for anything containing personal data, use one of the on-device tools instead.
Field data is missing for low-traffic pages, and repeat lab runs vary by several points on unchanged code.
Alternatives
Same category or same task, ordered by how closely they overlap.
webpagetest.org
Loads your page from a chosen city and browser and films the result
ssllabs.com
Grades a site's TLS configuration from A+ down to F and says why
securityheaders.com
Grades the HTTP security headers a site sends and names the missing ones
wave.webaim.org
Overlays accessibility errors directly on top of the page they affect
downforeveryoneorjustme.com
Settles whether a site is actually down or only down for you
lookup.icann.org
The registry's own WHOIS record for a domain, with no upsell