A quick one I built recently. Stick drift — when an analog stick reports input while it's sitting centred — is the most common way a game controller dies, and it turns out you can detect it from a web page with no native code at all, thanks to the Gamepad API. So I made a free tool that does exactly that and returns a plain pass/fail verdict instead of a wall of raw numbers.
What stick drift actually is
An analog stick reports its position as two numbers, X and Y, each running from roughly -1.0 to +1.0. At rest, both should sit at 0.0. Stick drift means that at rest the stick reports a non-zero value — say X = 0.18 — so the game thinks you're pushing the stick when your thumb is nowhere near it. The cause is usually a worn or contaminated potentiometer inside the stick module: dust, or just mechanical wear after a few thousand hours.
The thing most "how to test" guides get wrong: a tiny non-zero reading is normal. Every analog stick has a little electrical noise. The question isn't "is the resting value exactly zero" — it never is — it's "is the resting value large enough that the game will register it as input." That threshold is what separates a healthy stick from a drifting one.
The Gamepad API part
