Motion Sensor Test

There are several common causes. First, make sure you are using a device with built-in motion sensors (most smartphones and tablets have them; desktop computers and most laptops do not). Second, this tool must be served over HTTPS — browsers block access to device sensors on plain HTTP pages for security reasons. Third, on iOS 13 and later, Safari requires a user gesture to request permission before DeviceMotion events are available; tap the permission button on the page if shown. Fourth, some browsers on Android may require the page to be in the foreground and fully active.

An accelerometer measures linear acceleration — changes in velocity along the X, Y, and Z axes, including the constant acceleration due to gravity. When a device is lying flat and stationary on a table, the accelerometer reads approximately 0, 0, 9.8 m/s² (gravity pulling downward). A gyroscope measures angular velocity — how fast the device is rotating around each axis, expressed in degrees per second (°/s). Gyroscopes are unaffected by gravity and linear movement; they only detect rotation. Together, the two sensors complement each other to provide a full picture of device movement.

The accelerometer reports values in meters per second squared (m/s²). At rest on Earth, the total magnitude is approximately 9.8 m/s² due to gravitational acceleration. The gyroscope reports angular velocity in degrees per second (°/s); some systems use radians per second instead. The DeviceOrientation API reports orientation angles in degrees: alpha is the compass direction (0–360°), beta measures front-to-back tilt (−90° to +90°), and gamma measures left-to-right tilt (−90° to +90°).

Prior to iOS 13, Safari granted web pages automatic access to DeviceMotion and DeviceOrientation events without asking the user. Researchers demonstrated that these sensors could be exploited to identify walking patterns, infer PIN codes typed on a keyboard, and extract other sensitive behavioral data, raising significant privacy concerns. Apple responded in iOS 13 by requiring websites to explicitly request user permission via the DeviceMotionEvent.requestPermission() API, which must be triggered by a direct user action such as a button tap. This permission is session-scoped and must be requested again on each page load.

The DeviceOrientation API fires the deviceorientation event and reports the physical orientation of the device in space as three angles: alpha (rotation around the vertical/Z axis), beta (tilt around the X axis), and gamma (tilt around the Y axis). It describes where the device is pointing, not how it is moving. The DeviceMotion API fires the devicemotion event and reports the actual forces acting on the device: acceleration (with and without gravity) from the accelerometer, and rotation rate from the gyroscope. DeviceMotion is better suited for detecting shakes, steps, and directional movement, while DeviceOrientation works well for compass-style heading and tilt-based interfaces.