How to test your joystick
- Plug the stick into a USB port on the computer itself, plus the throttle and rudder pedals if they are separate devices. Move each one or press a button: browsers only reveal a device once it sends input.
- Check that the right device is picked as the stick, then set the twist and throttle: for known sticks this happens by itself, for others choose Find and move the control. The twist and throttle can sit on a different device, such as a separate HOTAS throttle.
- Press every button and push each hat switch into all 8 directions. Each one gets a mark, so a dead button or a direction that never registers stands out.
- Run the three health tests, then read or share the joystick health report.
Reading the results
Centre and drift is how far the stick rests from centre when you let go, as a percentage of full travel, with the jitter of the readings and the smallest deadzone that hides it. Flight sticks have strong centring springs, so a stick that settles well away from centre usually has a worn spring, a loose gimbal or a worn sensor. The same check covers the twist axis when one is set.
Full range records the furthest the stick reaches left, right, up and down. Each direction should reach 100%. A stick that stops at 90% in one direction limits your roll or pitch rate in that direction; recalibrating often fixes it (on Windows: joy.cpl, Properties, Calibrate). The outline on the plot shows the shape of the gate: most flight sticks have a square-ish range, so the corners reach further than on a round gamepad stick.
Axis smoothness is for the axes you move slowly and precisely: the throttle, the twist, sliders and rudder pedals. Move one from end to end over two or three seconds. The plot should rise steadily; a ringed spike (a reading that leaps and comes back) or a jump is the typical sign of a dirty or worn potentiometer, and a flat spot is a stretch where the output stood still while you kept moving.
How browsers see a joystick
Browsers read joysticks through the Gamepad API, but how they number things differs, which is why this tester lets you choose and find each axis:
- Axes. Chrome and Edge on Windows and macOS, and Firefox on Windows, give each axis a fixed slot by its HID type (X = 0, Y = 1, Z = 2, Rx = 3, Ry = 4, Rz = 5, slider = 6, dial = 7, wheel = 8) (Chromium source). A twist is usually Rz (axis 5) and a throttle slider axis 6, with unused slots reading 0. On Linux the axes are numbered in order instead.
- Hat switches. Chrome turns a hat into a single axis, axis 9 on most sticks: −1 is up and each 45° clockwise adds 2/7, and "centred" reads outside −1 to +1 (often 1.29 or 3.29). The tester decodes this into a direction rose. On Linux a hat arrives as two axes that jump between −1, 0 and +1, and Safari leaves hats and sliders out altogether (WebKit source).
- Limits. Chrome and Edge report at most 16 axes and 32 buttons per device (Chromium source). Firefox on Windows also stops at 16 axes but has no 32-button limit, so it shows the extra buttons of 64- and 128-button sticks (Firefox source).
- Output. The API has no force feedback, LEDs or displays, so those need the maker's software.
Fixing common problems
- Stick drifts or doesn't centre: recalibrate in the maker's software or joy.cpl, then run the centre check again and set the recommended deadzone in your game.
- Throttle or twist spikes: with the device unplugged, spray electrical contact cleaner into the potentiometer and move the axis end to end a few dozen times. If the spikes return, replace the potentiometer or fit a Hall-effect sensor kit.
- Buttons press themselves or a device disconnects: use a USB port on the computer rather than a hub, avoid long extension cables, and turn off USB selective suspend in Windows' power settings.
Gamepads have their own controller tester with a button diagram and rumble test, and racing gear has the steering wheel tester for wheels, pedals and shifters. To test how quickly you react, try the reaction time test.