Mouse Scroll Wheel Test
Diagnose scroll jitter, reverse scrolling, and skipping. Pick a duration, hover over the box, and scroll one direction to get your scroll speed, up/down counts, and a wheel-health verdict.
Scroll to start
Hover here and scroll your wheel one direction for 15 seconds.
Scroll speed over time
15s testInside almost every scroll wheel sits a rotary encoder that turns the wheel’s rotation into discrete electrical pulses — one per notch, or several on high-resolution wheels — each telling the computer to scroll a step up or down. When its contacts get dirty or wear out, those pulses come through wrong: the page jumps backwards mid-scroll, stutters, skips steps, or stops responding one way. Catching that misreporting is what this test does.
The test listens to your browser’s wheel events. Scroll steadily in one direction inside the box: the first tick locks that direction and starts the timer, and every tick after is counted and timestamped. Your scroll speed is ticks per second, and any tick firing the opposite way is logged as a reverse event — the clearest signature of a failing encoder. Everything runs locally in your browser.
A healthy wheel produces zero (or near-zero) reverse events and a fairly even speed graph. One stray reverse tick in a long, fast run can just be your finger easing off the wheel; a genuine fault keeps accumulating reverse events and repeats on every run. Also check the up/down split — if one direction barely counts while the other works, one encoder channel is likely dead, even when the reverse count looks fine.
Common scroll wheel faults
| Symptom | How it shows in the test | Likely cause |
|---|---|---|
| Reverse scrolling | Reverse count climbs steadily on every run | Dirty or worn encoder contacts misreading direction |
| Jitter and stutter | Uneven, spiky bars on the speed graph | Debris in the encoder or a worn detent mechanism |
| Skipped scrolls | Fewer ticks than the notches you can feel | Encoder missing steps; low battery on wireless mice |
| Dead direction | Up or down barely counts while the other is normal | One encoder channel has failed |
| No response | No ticks register at all | Fully failed encoder, or a driver/software issue |