What goes wrong in this category
Input devices fail in a way that is unusually hard to diagnose: the symptom appears in an application, but the cause can sit anywhere between the switch under your finger and the software you are typing into. A dead key, a double-clicking mouse and a trackpad that ignores gestures all look like application problems from the inside of an application.
A browser is a useful place to cut that chain roughly in half. Everything below it, the switch, the controller inside the device, the cable or wireless link and the driver, either delivers an event or does not. Everything above it, the keyboard layout, the game, the overlay, the macro utility, can only change what an event means, not whether it arrives. So a device that responds here and fails in one application has working hardware, and one that does not respond here has a problem below the browser.
What none of these tests can do is name the component. They see the presence, absence and timing of events, which is enough to tell a bouncing switch from a human hand and a missing keypress from a wrong character. It is not enough to tell a worn potentiometer from a dirty one, and no test on this site claims otherwise.
Which test for which symptom
| Symptom | Test | What it tells you |
|---|---|---|
| A key does nothing at all | Keyboard Test | Whether the press reaches the browser, which separates a dead switch from software swallowing it |
| A key types the wrong character | Key Code Viewer | Whether the physical key matches what you pressed, which points at the keyboard layout rather than the hardware |
| One click registers as two | Mouse Test | The gap between the two clicks: a few milliseconds is a bouncing switch, a few hundred is your hand |
| Scrolling goes the wrong way or not at all | Mouse Test | The direction and size of each wheel delta the browser receives |
| The trackpad ignores gestures | Touchpad Test | Whether movement, clicks and gestures arrive separately, which usually points at the driver |
| The controller moves on its own | Gamepad Test | The resting value on each stick axis, which is exactly what drift is |
Compiled by MyGearCheck. The last column is deliberately bounded: these tests observe what reaches the browser, which is enough to separate hardware from software and not enough to name a failing component.
Guides for input devices
A test tells you what is happening. These explain what to do about it, including when the honest answer is that nothing is wrong.