Gyroscope Test

About the Gyroscope Test

A gyroscope that has gone wrong shows up in small ways: a game that drifts to one side, a panorama that will not stitch, a compass that points the wrong way, a screen that rotates when it should not. This page reads the sensors your browser is allowed to see and shows exactly what they report.

You get the three orientation angles — the turn that gives the compass heading, the front-to-back tilt and the left-to-right tilt — as live numbers, plus a bubble level and a compass dial whose N keeps pointing north as you turn, so a drift is visible rather than something you have to read off a list. Where the browser offers them you also get the rotation rate in degrees per second and the acceleration in metres per second squared, and the page counts how many updates a second the sensors deliver.

Motion sensors are private, so a browser asks before a page may read them: on a phone there is a button below, and on some browsers the page must be loaded over a secure connection. A desktop computer usually has no orientation sensor at all, and the page says so instead of showing zeros.

What the three angles mean

The browser reports orientation as three angles:

• Alpha — the turn around the vertical axis, 0° to 360°, counted anticlockwise. The compass heading the page shows is the other way round, clockwise from north (360° minus alpha, or the browser’s own compass heading where it gives one). When the reading is absolute it is measured against north; otherwise it is measured from wherever the device was when the page started, so only changes mean anything.
• Beta — the front-to-back tilt, −180° to 180°. Flat on a table is 0°, upright in portrait is about 90°.
• Gamma — the left-to-right tilt, −90° to 90°. Rolling the device on to its right side gives a positive number.

Away from flat combines beta and gamma into one figure: how far the device is from lying flat, in degrees. Rotation rate comes from the gyroscope itself and is how fast the device is turning around each axis right now, in degrees per second — it is zero when the device is still, however it is tilted. Acceleration with gravity is what the accelerometer measures: at rest one axis reads about 9.8 m/s², which is gravity.

If nothing appears

• Allow motion access. Phone browsers ask for permission, and the sensors stay silent until you agree. If you refused, allow motion for this site in the browser’s settings for this page and reload.
• Use a secure connection. Browsers only expose motion sensors on a secure page.
• Check the device has the sensor. Desktops and most laptops have no gyroscope; some budget tablets have an accelerometer but no gyroscope, so tilt works and the rotation rate stays empty.
• Leave battery saver off. Some phones cut the sensor update rate sharply to save power, which shows up as a very low updates-per-second figure.
• Calibrate the compass by moving the device in a figure of eight; a heading that is steady but wrong is usually a compass that needs that, or a magnet in a case or holder.

Limitations

• The browser must be allowed to read motion sensors, and most phone browsers ask. Nothing can be read if permission is refused.
• A compass heading is only measured against north when the browser reports it as absolute; otherwise it is relative to where the page started.
• Browsers limit the sensor update rate — often to about 60 per second — and some reduce it further to make fingerprinting harder.
• A device with an accelerometer but no gyroscope shows tilt without a rotation rate. The page shows what arrives and nothing more.
• This cannot calibrate a sensor: it measures what the sensor reports, which is what you need in order to know that calibration is the problem.

Privacy

Sensor readings stay in this browser: they are drawn on the page and nothing is uploaded, stored or kept after you close it. Motion access is asked for by the browser, not by us.