GPS Speedometer Help Documentation

A complete guide to the GPS Speedometer, from the first reading to a saved trip.

Last Updated: November 13, 2026

1. Getting Started

The tool has four tabs: Drive (the speedometer), Trips, Tools and Settings, with How it works beside them. The round button at the top right switches the site between light and dark; the dial follows it.

Before your first drive, tap the vehicle in the dial's top right corner to choose what you are in, and the round sign at the top left to set your speed limit. Then press Show my speed. To see everything working without moving, press Try a demo drive.

2. Showing Your Speed

Press Show my speed and allow location when the browser asks. This is the only page of the site that may ask; nothing else on the site, and nothing embedded in this page, can read your location. The lamp above the dial blinks amber while the phone finds your position and turns green with the accuracy in metres once readings arrive. Press Stop GPS to stop reading the location.

• iPhone: Settings, Privacy and Security, Location Services, your browser: choose While Using and turn on Precise Location.
• Android: Settings, Location: turn it on and allow your browser to use it, with precise location.
• Laptops usually find their position from Wi-Fi networks and often report no speed; the tool then works it out from the change of position, a few seconds late.

Most phones stop giving websites the location when the screen goes off or the browser moves to the background, so keep the page open with the screen on; the tool keeps the screen on during trips unless you change that under Settings, Screen.

3. The Dial

The big number in the middle is your speed and the needle glides towards it. The red arc starts at your speed limit. A thin second needle stays at the trip's top speed (Settings can turn it off). The round sign at the top left shows your limit and opens the limit picker; the button at the top right shows your vehicle. Under the speed, the odometer rolls like a car's: tap it to show this trip, Trip A, Trip B or the total. Under the dial, the strip is a compass of where you are heading; GPS only knows your heading while you move. The dial's range follows the vehicle, or the value you choose under Settings.

4. The Trip Computer and Meters

Beside the dial (under it on a phone), This trip shows the distance, the time since the start and the time on the move, the average while moving and with stops, the top speed and when it happened, climb and descent, the GPS height, the acceleration in g and the time spent above your limit. Under them, Trip A, Trip B and Total count distance whenever real GPS shows you moving, like a car's meters; Reset sets Trip A or B back to zero. The Speed chart shows the last 2 or 10 minutes, or the whole trip, with your limit as a line and any speed above it in red.

On foot, the pace (minutes per kilometre or mile) shows under the speed and the distance.

5. The Speed Limit Warning

Pick a limit from the sign or under Settings, Speed limit warning, where you can also turn the warning off, step the limit up or down and choose a margin (Warn when over by). Above the limit plus the margin the dial turns red, the sign pulses and you hear a chime or three beeps (or nothing), feel a vibration on Android phones and, if you turn it on, hear "Slow down". While you stay above it, the warning repeats every 12 seconds. Hear the warning plays it. The limit is one you set yourself, not a map of real limits: the road signs always apply.

6. Recording a Trip

With your speed showing, press Start trip. Pause stops the clock at a stop and Carry on restarts it; Finish shows a summary and a name made from the time of day and the kind of trip, such as Morning drive. Save trip keeps it under Trips; Discard throws it away after you confirm; Keep going returns to the trip. Settings, Trips and GPS can start a trip by itself once you move off, and can say the distance, time and average every kilometre or mile.

A trip recorded from real GPS is kept in this browser every few seconds. If the page closes, the next visit asks whether to carry on (the time away counts as a pause), save it as it is, or discard it.

7. Laps

During a trip, Lap (or the L key) closes a lap and starts the next. The Laps card lists each lap's time, distance, average and top speed, newest first, with the fastest marked. Settings, Trips and GPS can start a lap every 1, 5 or 10 kilometres or miles, and can say each lap time aloud. A saved trip with laps gets a last part lap so the laps add up to the whole trip.

8. Big Digits, Windscreen and Camera

• Big digits fills the screen with your speed, a bar and your limit, for a phone in a holder.
• Windscreen does the same with the figures mirrored: at night, lay the phone flat on the dashboard under the windscreen, top edge towards the glass, and read the reflection. Mirror switches between up and down and left and right.
• In both, tap the screen for the controls: Colour (green, white, amber or blue), Brightness and Close (or Esc). The screen stays on while they are open.
• Camera shows the camera picture with your speed, the date and time, your heading and your limit on top. The red button records a video and Photo takes a picture, both with those figures burned in; Position adds your coordinates; Turn switches cameras. Files are saved straight to your device and never uploaded.

Opening any of the three starts the location if it is not running yet.

9. The Demo Drive and Replays

Try a demo drive plays a made-up drive of about four and a half minutes, with traffic lights, a hard launch, a hill, an overtake and a slip road, at 1x, 4x or 10x speed. Everything works as with real GPS, including recording it as a trip (saved with "(demo)" in its name), but the meters do not count it and the location is not used. Replay on a saved trip plays it back on the dial at 10x; nothing is recorded again.

10. The Trips Tab

Trips lists every saved trip, newest first, each with a small outline of its route, its date, distance, time, average and top speed. The tiles at the top add up the trips shown, and with more than one kind of vehicle the chips filter by vehicle. Trips from GPX files and from the demo carry a label.

11. One Trip in Detail

Open a trip to see its tiles (distance, time, averages, top speed, climb, highest and lowest point, stopped time and time over the limit), its route coloured by speed with a start, a finish, the top speed, a scale and north, the speed and height charts by distance or by time, the time at each speed (also as a table), splits for each kilometre or mile with the fastest marked, and its laps. Point at the route or a chart to see the speed, distance and time there. Click the name to rename the trip. The route is drawn from your own points with nothing underneath, so nothing about where you went is fetched.

12. GPX Files, Backups and Exports

• Open a GPX file reads tracks, routes or waypoints with times from a watch, bike computer or another app, up to 30 MB a file. Speed comes from the file when it has it, otherwise from the track. The kind of trip is guessed from the speeds.
• A trip's buttons save it as GPX (with speeds), KML, CSV or GeoJSON.
• Back up all trips saves one file with every trip and your timer results; Restore a backup reads it on any device (up to 300 MB), skips trips already there and checks every value first. Backups from the earlier version of this speedometer are read too.

13. Performance Timer

Use it only on a closed road or a track, never in traffic. Choose a test: 0 to 50, 0 to 100 and 0 to 200 km/h (or 0 to 30, 60 and 100 mph), rolling tests such as 60 to 100 or 80 to 120 km/h, braking from 100 km/h (60 mph), the eighth mile, quarter mile and one kilometre, or your own speeds. Press Get ready and follow the line above the clock; the clock starts on its own when you move off or pass the start speed, and stops at the target. The start of a standing launch is worked out back from the first readings, and every crossing between readings, so times are not limited to whole readings. Tick the one-foot rollout to leave out the first 30 cm. The braking test ends when the speed falls below about 1 km/h. Results (up to 40) stay on this device with their speed curve; the fastest of each test is marked, and demo runs are labelled. Try it with the demo drive shows a 0 to 100 run.

14. Speedometer Check and Average Speed Check

Speedometer check: with a passenger, hold a steady speed above 20 km/h (20 mph or 20 knots in those units) until the GPS figure says Steady; the passenger types what the car's speedometer shows and presses Compare. With each reading the tool says how far your speedometer reads high or low. Car speedometers may read high but never low (UN Regulation No. 39 allows up to 10 percent plus 4 km/h more); reading low can mean you are going faster than you think.

Average speed check: for roads with average speed cameras. Press Start at the camera as you pass the first one; the average so far and the distance follow. With the zone length typed, Keep under shows the speed that keeps your average under the limit for the rest of the zone, never more than the limit itself. Press Stop at the last camera for your final average.

15. G-meter and Where Am I

G-meter: speeding up moves the dot up, braking down, bends left and right, with a short trail and the strongest pull ringed. From GPS works it out from changes in speed and heading about once a second; Motion sensor reads the phone's accelerometer (iPhones ask first): hold the phone still in a mount and press Set level here while stopped. If the dot moves the wrong way, drive a little and the tool learns the direction from GPS.

Where am I shows your position as a Plus Code, as latitude and longitude, and in degrees, minutes and seconds, with the height and accuracy, to read out on a phone call. Copy and Share send it only where you choose.

16. Settings and Your Data

Settings has six cards: Vehicle and units, Speed limit warning, Spoken updates (only voices stored on your device are offered), Trips and GPS, Screen and Your data. Changes are saved at once. Choosing Boat switches to knots; mph switches heights to feet unless you chose the height unit yourself.

Settings, the meters and timer results are kept in this browser's storage, and trips in its own database on this device. Nothing is saved on a first visit until you change something or record a trip. Delete, under Your data, removes every trip, timer result and speedometer reading after you confirm; the settings stay. Data from the earlier version of this speedometer in this browser is moved over once. Browsers can clear a site's data when a device runs low on space, so back up trips you want to keep.

17. Keyboard and Accessibility

Every button and field works with the keyboard. The tabs are a tab list: the arrow keys, Home and End move between them. On the Drive screen, while you use the tool and are not typing, Space starts or pauses a trip once your speed is shown, L marks a lap, B shows big digits and W the windscreen view; Esc closes them. Space never asks for your location. Elsewhere on the page these keys do what they always do. Screen readers announce the warnings, trip changes and laps, and can read the current speed under the dial. With reduced motion set on your device, the dial does not sweep at the start and nothing blinks or pulses.

18. Safety

• Keep your eyes on the road. Set everything up before you drive, or let a passenger use the speedometer.
• Use a proper phone holder, and follow your country's rules on phones in vehicles.
• Use the performance timer only on a closed road or a track, never in traffic.
• The speed limit warning and the average speed check are reminders you set yourself. The road signs always apply, at every point of the road.

19. Privacy

The speedometer reads your location only after you press Show my speed or another button that needs your speed (Start trip, Big digits, Windscreen, Camera, Get ready or Start at the camera), and only while this page is open. Everything is worked out in this browser: your position, trips, photos and videos are never uploaded, and there is no account and no server-side storage. The route of a trip is drawn without a map, so nothing about where you went is fetched. Spoken updates use only voices stored on your device. Like every page on ZeroDataUpload, the page shows advertising and counts visits; the cookie banner explains the choices and the Privacy Policy explains both. Those scripts cannot read your location, and your position and trips are never part of them.

20. How It Was Checked

Before this page was published, the engine behind the tool was checked against independent references: 294,942 cases in 14 groups. They include the speed and distance units against their exact definitions, distances and bearings against an ellipsoid model of the Earth, Plus Codes against Google's own library, the performance timer against exact answers for steady acceleration at 1 to 10 readings a second (with and without the rollout), splits and the time at each speed, the GPX reader against the earlier version on 30,000 random files and on files made to slow it down, saved GPX files against the published GPX 1.1 schema, and saved data, backups and settings made to break the tool. Then the page was tried at four screen widths in both themes, with the location supplied by the test browser.

21. Troubleshooting

• "Location is blocked for this page". Allow location for zerodataupload.com in the browser's site settings and in the phone's location settings, then press Show my speed again.
• The lamp keeps blinking amber. Go outside or near a window; under a roof, in a tunnel or a multi-storey car park the phone may get no fix.
• The speed jumps or lags. Choose a stricter accuracy limit or Steady the dial under Settings, Trips and GPS.
• The trip stopped when the screen went off. Keep the screen on (Settings, Screen) and the page in front.
• No sound for the warning. Check the phone's volume and the Sound setting, and tap the page once: browsers allow sound only after you touch the page.
• A GPX file will not open. It needs at least two points with times; files over 30 MB are refused.
• My trips are gone. They are kept per browser and device; a private window or cleared browser data starts afresh. Back up your trips to keep a copy.

22. Support

For questions the FAQ does not answer, use the contact form.