GPS Accuracy Test
Measure how precise your location fix is — without ever reading where you are.
How this test works
The Geolocation API is watched continuously and every fix's accuracy value is recorded, while the coordinates themselves are discarded on arrival — they are never displayed and never leave the page, because the question here is the size of the uncertainty rather than where you are. The accuracy figure is the part worth understanding: it is a radius at 68% confidence, so a fix reporting 20 metres means about a two in three chance of being inside that circle, not a promise. The likely source is inferred rather than reported, because no platform says. Altitude is the strongest available clue — only a real satellite fix produces it, since wifi and cell positioning cannot — so a fix with altitude and a tight radius is almost certainly GNSS.
What the results mean
- Best accuracy
- The tightest radius seen. The first fix is usually the worst; it improves as more satellites resolve.
- 68% confidence radius
- What the accuracy number means. Two times in three you are inside it, once in three you are not.
- Likely source
- Inferred from the radius and altitude. Under about 30 metres with altitude means satellites.
- Altitude reported
- Only GNSS produces it. Its presence is the best evidence available that satellites are involved.
Common problems and fixes
- Accuracy is hundreds of metres
- You are almost certainly indoors on wifi or cell positioning. Satellites need sky view; move outside and away from tall buildings and watch it tighten.
- It never improves
- Some devices cache a coarse fix and return it repeatedly. Waiting thirty seconds outdoors usually forces a fresh satellite fix.
- Why does the page not show my location?
- Because it does not need it. The coordinates are discarded as each fix arrives — only the accuracy figure is kept.
Frequently asked questions
What does the accuracy number actually mean?
It is a radius at 68% confidence. A value of 10 metres means roughly a two in three chance you are within 10 metres of the reported point, and a one in three chance you are further away. It is not a maximum error.
Why is my phone more accurate outdoors?
Because satellite positioning needs a clear view of the sky. Indoors the device falls back to wifi access points, which is typically tens of metres — though indoors that is often better than a weak satellite fix would be.
Does this page know where I am?
No. The coordinates are discarded on arrival and never rendered or transmitted. Only the accuracy radius is retained, and only in the page.