Lighthouse performance score
The 0-100 number, from the same engine as pagespeed.web.dev, so it matches what anyone else checking will see.
Free tool
How fast is it, really — on a phone?
A real Lighthouse audit via Google's own API, not an estimate. You get the Core Web Vitals that decide rankings, how much each one is costing you, and the specific changes that would move the number most.
What it checks
Everything in one pass.
Core Web Vitals
LCP, CLS and Total Blocking Time, each shown with how much of the score it controls — TBT alone is 30%.
Why each metric matters
Plain-English explanation of what causes each one to be slow, rather than a metric name and a number.
Real visitor data
When Google has enough Chrome traffic for the site, the field data it actually ranks on — not just the lab simulation.
Biggest wins first
Opportunities sorted by estimated saving, so you start with the change worth 800ms rather than the one worth 20.
Mobile and desktop
Both available, defaulting to mobile because that is what Google indexes on and where the problems are.
Questions
What this tool is, and is not.
- Where do these numbers come from?
- Google's PageSpeed Insights API. It is the same engine behind pagespeed.web.dev, running a real Lighthouse audit in a throttled Chrome on Google's infrastructure — not a stopwatch on a fetch from a data centre. The numbers match what your client will see if they check for themselves.
- Why does the score change between runs?
- Because it is a simulation on shared infrastructure, and identical code routinely swings a few points. Run it three times and take the middle. A two-point movement is noise; a twenty-point movement is real.
- What is the difference between the score and the real-visitor data?
- The score is a lab simulation of one page load on a mid-range phone. The real-visitor section, when it appears, is aggregated from Chrome users who actually visited over the last 28 days — and that is what Google uses for ranking. Sites with little traffic will not have it.
- Why mobile by default?
- Because Google indexes and ranks on mobile, and mobile is where sites are slow. A desktop score of 100 next to a mobile score of 45 is a common and misleading pairing.
Know the number, unsure what to do about it?
Most speed problems come down to three or four decisions made early. Send the report and I will tell you which ones are costing you, and which of the opportunities listed are not worth the effort.