Phone Sensor Test
Check the accelerometer, gyroscope and compass on a phone or tablet. Tap Start, then tilt it, spin it and point it north — a sensor that is dead, stuck or wildly off becomes obvious in seconds. All readings stay on your screen.
What each sensor does
The accelerometer measures acceleration on three axes and always includes gravity, so a phone lying perfectly still is never reading zero — it reads the 9.8 m/s² pull of the Earth. That is what makes it useful: the direction of that constant pull tells the phone which way is down, and it is how your screen knows to rotate. The gyroscope measures how fast the phone is turning, in degrees per second, and it is what keeps a game steady when you tilt it. The magnetometer measures the Earth's magnetic field and gives a heading, which is the compass.
How to read the numbers
Start with the accelerometer on a flat table. One axis should read close to +9.8 or −9.8 and the other two close to zero. Tip the phone onto each of its four sides in turn: the big number should move to a different axis each time, and the total should stay near 9.8. A total that drifts away from 9.8, or an axis that stays large when it should be near zero, is the signature of a faulty accelerometer.
Then the gyroscope. Put the phone down and watch: small residuals under about 1°/s are normal sensor bias and mean nothing. A steady offset of several degrees per second, or numbers that creep while the phone lies untouched, is real. Rotate the phone slowly through a full turn and back to where it started — a healthy gyroscope returns to roughly where it began.
When a reading is actually wrong
A compass is the one reading that lies for innocent reasons. The browser is one of them: some report an absolute heading, others an angle from an arbitrary reference, and the compass card warns you when the heading you are seeing is the second kind. The world around you is the other: steel desks, car doors, speakers, magnetic cases and wireless chargers all bend the Earth's field locally, so an indoor heading can be tens of degrees off on a perfectly good phone. Test outdoors, away from metal, and recalibrate with the figure-eight gesture before you suspect hardware. If the heading is wrong everywhere — confirmed against a known compass, not just against the browser's own reference — or the accelerometer total ignores gravity, the phone has a real sensor fault worth a repair claim. A clean reading here also settles the opposite question: when an app or a game misbehaves, a working sensor rules the hardware out. The methodology page explains how every test on this site is built and what it can and cannot prove.
Frequently asked questions
What should the accelerometer read when the phone is still?
About 9.8 m/s² in total, and that is gravity rather than movement. Lying flat on its back, a phone reads close to 9.8 on one axis and near zero on the other two. Turn it on its side and the big number moves to a different axis. A still phone reading well away from 9.8, or drifting while it sits untouched, points at a failing sensor.
The gyroscope values are not exactly zero at rest. Is it broken?
No. Tiny residuals, usually under 1 degree per second, are normal bias in a cheap MEMS sensor and mean nothing. A real fault reads as a steady offset of several degrees per second, or values that creep while the phone lies perfectly still. Rotate the phone through a full turn and back: a healthy sensor returns to roughly where it started.
Why does the compass point the wrong way?
Not always the sensor, and not always interference — rule out the browser first. Some browsers report a heading relative to true north, others an angle from an arbitrary reference, and the second kind reads as a constant offset no matter where you point; the compass card warns you when that is the case. Compare the reading against a known compass before blaming hardware. The rest is interference: magnets in a case, a magnetic car mount, a laptop speaker or a wireless charger all pull the reading off, so test away from metal and recalibrate with the figure-eight gesture. A heading that is only wrong in one place is interference; one that is wrong everywhere, against a known compass too, is the sensor.
Why do I get no readings on my iPhone?
Safari blocks motion sensors until you grant permission, and it only asks after a tap, which is what this page's Start button provides. If you denied it once, reload and tap Start again. The sensors also require HTTPS, so a page served over plain HTTP cannot read them at all.
The readings freeze as soon as I switch apps. Is the test broken?
No. Browsers throttle motion sensors in background tabs to save battery, so readings stop updating the moment the page is hidden and resume when you come back. That is a browser policy, not a fault in your phone.
Can this test tell me whether my phone has been dropped?
No, and it does not try to. It shows whether the sensors work now, not what happened to them. A phone that has had a hard knock but reports clean values is fine; one with a stuck axis is not, whatever its history.
Does the compass work indoors?
Poorly, and that is expected. A magnetometer measures the Earth's magnetic field, which building steel and electronics distort, so indoor headings can be tens of degrees off on a good phone. Test the compass outdoors, away from cars and buildings, for a reading worth trusting.
Is any of this data sent anywhere?
No. Sensor values are read in this tab and drawn on screen. Nothing is stored, uploaded or shared, and closing the page ends it.