The short version: an accelerometer measures linear acceleration plus gravity, so it answers "which way is down, and am I being moved?". A gyroscope measures angular velocity, so it answers "how fast am I rotating around each axis?". Your phone fuses both into one stable orientation estimate.
You can verify each sensor in about a minute, no app install: run the browser accelerometer test with the phone flat on a table (Z should read about 9.8 m/s²), then rotate the phone in the gyroscope test and watch alpha, beta, and gamma move.
Full guide with the fix list and FAQ:
Accelerometer vs Gyroscope: What's the Difference? (Test Both in Your Browser)
The comparison at a glance
| Accelerometer | Gyroscope | |
|---|---|---|
| Measures | Linear acceleration + gravity | Rotation rate (angular velocity) |
| Units | m/s² | deg/s or rad/s |
| Reading at rest | ~9.8 m/s² on the "down" axis | ~0 on all axes |
| Answers | "Which way is down? Am I being moved?" | "How fast am I turning right now?" |
| Weakness alone | Jittery moment to moment | Drifts over time |
| Typical jobs | Auto-rotate, step counting, lift-to-wake, shake gestures | Gyro aiming, AR anchoring, video stabilization, panoramas |
Neither sensor is good enough alone. Accelerometer-only orientation jitters as you walk; gyroscope-only orientation drifts as small rate errors accumulate. Phones fuse the two (plus the magnetometer for heading) into the alpha/beta/gamma angles that browsers report through DeviceOrientationEvent.
Test the accelerometer (60 seconds)
- Open the accelerometer test on your phone.
- Lay the phone flat and still: expect roughly +9.8 m/s² on Z and near zero on X and Y.
- Tilt the phone and watch gravity shift between axes.
Failure patterns are just as clear. All axes stuck at zero usually means denied motion permission or a dead sensor. One axis pinned to a fixed value in every orientation is a hardware fault. Values jumping past 100 m/s² while the phone rests on a table point to a calibration or driver problem.
Test the gyroscope
Open the rotate-your-phone gyroscope test and rotate the phone around each axis. Alpha tracks flat spinning (like a compass needle), beta tracks front-to-back tilt, and gamma tracks left-to-right tilt. The on-screen 3D cube should follow your hand smoothly, without lag, jumps, or frozen angles.
Auto-rotate broken? Work down this list
Most "broken accelerometer" reports are software, not hardware:
- Check the rotation lock (Android Quick Settings auto-rotate; iPhone Portrait Orientation Lock).
- Restart the phone to clear stuck sensor services.
- Recalibrate with a figure-8 motion, then rest the phone on a flat surface.
- Try safe mode on Android to rule out a third-party app forcing orientation.
- On Samsung, dial
*#0*#and open the Sensor panel for live values. - If the browser test and the diagnostic panel still show flat or frozen values, the IMU chip or board connection has likely failed, often after a drop or screen replacement.
One boundary case worth knowing: if motion readings are fine but the screen taps itself or has dead spots, the problem is the digitizer, not the motion sensors. A touch screen test maps phantom taps and dead zones so you do not blame the wrong component.
Related browser checks
- Vibration test for the haptic motor
- Does my phone have a gyroscope? for a 10-second existence check plus PUBG/CODM/Pokemon GO gyro settings
Everything runs in the browser through standard DeviceMotion and DeviceOrientation APIs, so it works on Android and iPhone without installing anything.
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