Our own edge · geo-located servers · distance-limit detection
Now running against our own Cloudflare Worker rather than borrowing Cloudflare's public speed-test endpoints — which means we can see exactly which datacentre is serving you, and the diagnostics panel records it. It still asks M-Lab where your nearest measurement servers are, races every backend it can reach, and refuses to print a number as your line speed when the maths says distance capped it.
The full run takes about a minute and a half. You can leave the tab open and come back.