Mouse scroll wheel test
Scroll steadily in one direction inside the box. Every wheel event is counted; a single event in the opposite direction during a steady scroll is flagged, which is the typical sign of a jumping, worn scroll wheel.
Scroll slowly in one direction inside the box.
Scroll here: down only, then up only
- Up
- 0
- Down
- 0
- Reversals
- 0
- Sideways
- 0
- Wheel clicks
- 0
Last step: —
Recent events: blue = up, green = down, tall red = reversal.
Wheel log (last 80)
| ms | direction | delta | since previous |
|---|
How to run the test
- Point at the box and scroll down only, slowly, notch by notch, for 20–30 notches.
- Then scroll up only the same way.
- Repeat at normal speed and fast.
- Click the wheel a few times to test the middle button.
Reading the result
- Up and down counts match what you did and no reversals: the wheel encoder works in this test.
- Reversals: an event in the opposite direction while you were scrolling steadily one way. One or two during very fast flicks can happen; regular reversals at slow speed are the classic symptom of a worn or dirty encoder.
- Missing events: if you turned several notches but fewer events appear, the encoder skips.
- Delta and unit: the size of each step depends on your operating system, driver and settings (pixels, lines or pages). Smooth-scrolling touchpads and free-spinning wheels send many small events; that is normal.
Fixes worth trying
- Blow compressed air into the gap around the wheel while turning it; dust in the encoder is a common cause of jumping.
- Check the mouse software for a smooth-scroll or acceleration setting, and test in a different browser.
- If the wheel keeps reversing, the encoder is worn. It is a common warranty fault on many mice.
Questions
Why does my scroll wheel jump up when I scroll down?
The wheel encoder reads the wrong direction for a moment, usually because of wear or dirt. This test counts those events so you can confirm it and check whether cleaning helped.
Does it work with a touchpad?
Yes, two-finger scrolling also sends wheel events, but in many small steps. Reversal flags are most meaningful for notched mouse wheels.