Gyroscope and accelerometer test

What is being read

A modern phone carries three separate pieces of hardware that this page reads.

• The accelerometer measures force, including gravity. It is how a phone knows which way is down.
• The gyroscope measures rate of rotation. It is what makes a game camera follow the phone smoothly.
• The magnetometer is the compass, reading the magnetic field.

Tilt the device and the block on screen should follow it. If it does not move at all, or moves on the wrong axis, that is the finding.

If nothing happens on an iPhone

This is the most common problem with sensor pages, and it is not a fault. Since iOS 13, Safari requires explicit permission for motion data and will only ask when a page requests it from a button press. Without that request the events simply never arrive - no error, no prompt, nothing. That is why this page has a Start button. Press it and accept the prompt.

Two further requirements: the page must be served over a secure https connection, and in Safari settings "Motion & Orientation Access" must be enabled.

On a desktop

Most desktop computers and monitors have no motion sensors, so blank readings there are expected rather than a fault. Some convertible laptops and tablets do report orientation.

The drift check

Put the device flat on a table, do not touch it, and press Check for drift. A healthy gyroscope reports close to zero rotation when nothing is moving.

• Under 2 degrees per second - normal. Every sensor has some noise.
• 2 to 5 - slight drift. Usually harmless, and recalibrating often clears it.
• Over 5 - the phone believes it is turning while sitting still. This is what makes a compass wander, a map rotate on its own and a camera creep in a game.

To recalibrate, move the phone slowly in a figure of eight a few times, away from speakers, magnets and magnetic phone mounts - a magnetised case is a common cause of a compass that will not settle. Restarting the phone also re-runs the calibration routine.

Reading the axes

Alpha is rotation about the vertical axis - compass direction. Beta is front-to-back tilt. Gamma is left-to-right tilt. The compass heading is shown separately where the device reports a true heading rather than a relative one, because those are not the same reading and treating them as interchangeable is a common mistake.

A dash means that sensor has never reported a value, which is different from a reading of zero - a phone lying flat genuinely reads near zero on two axes, and showing a confident 0.00 for hardware that is absent would be misleading.

Privacy

All readings stay in your browser. Nothing about your device movement is transmitted or stored.