A residency claim has a speed limit.
Light in fibre covers roughly 100 km for every millisecond of round trip. So if something answers you faster than the distance allows, it is not where you were told it is — or it is not the thing you were told about. Measure it yourself, from your own browser, against any vendor.
A hostname or full URL. The request is made by your browser, to that host, and nothing about it reaches us — this page has no server side.
How the bound works
Light travels through glass at about two-thirds of its speed in vacuum — roughly 200,000 km per second. A round trip covers the distance twice, so one millisecond of round-trip time buys about 100 km of separation. That is a ceiling, not an estimate: real fibre does not run in straight lines, routers add delay, and the server takes time to answer. Whatever answered is no further away than the number this gives you, and almost certainly closer.
What it proves, and what it does not
It proves where the thing that answered you is. That is not always the same as where your data is, and the difference is the honest part of this tool.
- A fast answer is a question, not a verdict. A CDN or an anycast front end legitimately answers near you while the bytes sit elsewhere. That is normal engineering, not a broken promise.
- A slow answer proves nothing either. Distance sets a floor, not a ceiling: a nearby server can still be slow.
- The useful case is a claim that is too fast. If a vendor says data is only in one place, and something answers far quicker than that place allows, ask what answered. The answer is either a cache, an edge, or a copy — and all three are worth knowing about.
Why we published this
It works against us as readily as against anyone else, which is the point. A test you run yourself, on a vendor of your choosing, with a tool that shipped with your operating system, is worth more than any diagram we could draw. Sovereignty that depends on being believed is not sovereignty.
Then ask the harder question.
Where something answers from is one of five questions that decide whether data is actually yours. The other four are about who can read it, who can seize it, whether you could leave, and what is learning from it.