What is an online speedometer?
It's a speedometer that runs in your browser instead of sitting in your dashboard. Press Start, allow location, and you get your live speed on a car-style dial. Nothing to install and no account.
It works for anything that moves. A car, a motorbike, a bike, a run, a train, a ferry, a flight. You can switch between km/h, mph, knots and m/s, and your location never leaves your phone.
How does it work?
Your car counts wheel rotations. This doesn't touch your wheels at all. It asks your phone's satellite receiver where you are, several times a second, and works out how fast the ground is moving under you.
Most phones do something cleverer than just comparing coordinates. The GPS chip measures the Doppler shift in the satellite signal, which gives a speed reading directly and is much steadier. We use that whenever your phone reports it.
What the numbers mean
| Reading | What it tells you |
|---|---|
| Max | Fastest you've been since the last reset. |
| Average | Distance over total time. Traffic lights drag it down. |
| Distance | Ground covered, added up between fixes. |
| Elapsed | Time since you pressed Start, minus any pauses. |
| Moving | Time above walking pace. Compare it with Elapsed to see how long you sat still. |
| Accuracy | How close your phone thinks it is. Under ±10 m is good. |
| Altitude | Height above sea level. Always less accurate than your position. |
| Heading | Which way you're going. Only shows while you're moving. |
How accurate is it?
Outdoors with a clear sky, a modern phone gets within about 1 to 3 km/h. That's usually better than the dial in your car. But it falls apart in a few predictable places:
- Tunnels, car parks, indoors. No satellites, no reading. Your phone might switch to Wi-Fi positioning, which is useless for speed.
- Streets with tall buildings. The signal bounces off the walls and arrives late, so the number jumps around.
- Hard acceleration. You get roughly one reading a second, so a quick launch shows up slightly late.
- Battery saver. It throttles location updates and doesn't tell you.
- Where the phone is. Flat in a cupholder or in your pocket sees far less sky than a windscreen mount.
Keep an eye on the accuracy figure. If it's above ±50 m you're probably not on satellites at all.
How to use it
Set your speed alert before you set off. It draws a red zone on the dial and beeps once each time you go over.
- Open this on your phone and press Start.
- Allow location when the browser asks.
- Wait for the dot to turn green. The first fix can take 20 to 30 seconds outdoors.
- Press Reset once you're moving, to zero the trip.
- Tap the fullscreen icon for a big dashboard-style display.
Something not working?
Nothing happens when I press Start
- Check you allowed location. If you dismissed the prompt, reset it in your browser's site settings and reload.
- Location services need to be on in your phone settings too, not just the browser.
It says zero but I'm moving
- Go outside and wait for the first fix. Indoors, most phones never report speed at all.
- Look at the accuracy. Above ±50 m you're on Wi-Fi or cell positioning, not GPS.
- Try loosening the accuracy filter in settings.
Distance keeps going up while I'm parked
That's GPS drift being counted as movement. Set the accuracy filter to ±10 m and it goes away.
The needle is twitchy
Turn up the smoothing in settings. You get a calmer needle, and it reacts a little slower.
My screen keeps dimming
Turn on "Keep screen on". Some browsers ignore it, so set a longer screen timeout on your phone as well. And keep this tab in front, because phones suspend background tabs and that stops the measuring.
Frequently asked questions
Is it accurate?
Under open sky, yes. Roughly ±1 to 3 km/h, which is usually closer to the truth than your car's dial. It's not a legal or certified measurement though, and it gets bad indoors, in tunnels and between tall buildings.
Does it work without internet?
Yes. The page saves itself to your phone the first time you open it, so it loads with no connection. Speed comes from satellites, not from the network, so it keeps working where there's no data at all.
Do you store my location?
No. Everything is worked out in your browser and nothing is sent to a server. Close the tab and it's gone.
Why does my car show a higher number?
Because it has to. Speedometers are allowed to read high but never low, so carmakers set them a few percent over. A 5 to 10% gap at motorway speed is normal.
Can I use it for running or cycling?
Yes. It measures ground speed for anything. Runners usually want minutes per kilometre rather than km/h, and there's a separate running page for that.
Will it drain my battery?
GPS with the screen on is hard work for a phone. On a long drive, plug it in.
Why does it need location just to show speed?
Speed comes from position. Browsers hand out both through the same permission, so there's no way to get one without the other.