GPS Tester
Check your device's GPS and GNSS signal quality live in the browser. See coordinates, accuracy, altitude, speed, and heading without installing anything.
- Runs locally
- Requires permission
- No uploads
Location fix
This tool needs your location. Click Start and allow location access when your browser asks. Your coordinates never leave your device. All processing is local.
GPS Readout
About this tool
GPS Tester uses the browser Geolocation API to read your device's GPS or GNSS receiver and display live data: latitude, longitude, accuracy in meters, altitude, speed, and heading.
It also tracks the best (lowest) accuracy seen this session and computes the straight-line distance from your first fix using the haversine formula, useful for checking receiver drift or testing walk accuracy.
Your location data stays entirely on your device. Nothing is sent to any server.
What is GNSS?
- GPS: US satellite system, 24+ satellites, the original consumer standard.
- GLONASS: Russia's equivalent; most modern phones use both GPS and GLONASS simultaneously.
- Galileo: European system offering higher accuracy; supported by most flagship Android phones since 2018.
- BeiDou: China's GNSS; widely supported on phones sold in Asian markets.
- Accuracy: the reported radius in meters within which your true position lies with 68% probability.
Tips
- Move outdoors for the best fix. Clear sky view with no overhead obstructions gives the lowest accuracy figures.
- If accuracy stays above 50 m indoors, your phone is falling back to Wi-Fi or cell positioning, not true GPS.
- The first fix after a cold start can take 30-60 seconds. Subsequent fixes are faster because the receiver caches almanac data.
- Speed and heading are only reported while moving. Stationary readings may show null or zero.
- Use the Copy coordinates button to paste your location into a map app, spreadsheet, or bug report.
About the GPS Tester
Your phone has a dedicated GNSS receiver that pulls signals from dozens of satellites to compute a position. The accuracy that gets reported is not a measurement of error. It is a 1-sigma radius (68% confidence) estimated by the receiver's own Kalman filter based on satellite geometry and signal strength. An accuracy of 5 m means the receiver is 68% confident your true location is within 5 m of the reported point.
What the readings mean
The tool displays all seven values from the browser Geolocation API: latitude and longitude in decimal degrees (plus degrees-minutes-seconds), accuracy in meters with a quality label, altitude above the WGS-84 ellipsoid (where the device supplies it), speed in km/h, heading in degrees true north, and the timestamp of the fix.
Accuracy labels
The labels are: excellent for under 10 m (typical clear-sky GPS), good for 10-29 m, fair for 30-99 m, and poor for 100 m and above. Poor accuracy often means the device is using cell or Wi-Fi positioning instead of satellite signals.
Session tracking
The tool records the best accuracy seen since you clicked Start. It also uses the haversine formula to compute the straight-line distance from your first fix, which is useful for checking whether a receiver is drifting while stationary or for measuring a short walk.
Frequently asked questions
Why does GPS accuracy vary so much?
Signal quality depends on how many satellites are in view, their angles in the sky (geometry), and whether signals are bouncing off buildings or blocked by roofs. Outdoors in open sky you typically get under 5 m. Underground or in dense urban canyons accuracy can degrade to hundreds of meters.
Is my location data sent anywhere?
No. This tool runs entirely in your browser. The Geolocation API reads data from your device's hardware, and all processing happens locally. No coordinates are uploaded or logged.
Why are altitude and speed sometimes missing?
The Geolocation API marks altitude, speed, and heading as optional. Devices without a barometer often skip altitude, and speed and heading are only meaningful when you are moving. The tool shows "n/a" when the browser does not supply a value.
What is the difference between a warm start and a cold start?
A cold start happens when the receiver has no cached almanac or ephemeris data and must download it from scratch over the satellite signal, which can take 30-60 seconds. A warm start reuses cached data and gets a fix in a few seconds. Turning airplane mode on and off, or rebooting, can force a cold start.