How to test your scroll wheel
- Move your cursor over the box.
- Roll the wheel slowly and steadily in one direction for a few seconds.
- Watch the counters and the log. Every tick should register in the direction you rolled.
- Repeat in the other direction and at different speeds.
Signs of a failing scroll wheel
- Direction glitches: a single tick registers backwards in the middle of a steady scroll. The test counts these.
- Skipped ticks: you roll several notches but fewer events register.
- Page jumping: pages scroll up or down on their own while you scroll in one direction.
- Only one direction works, or the wheel registers only at certain speeds.
What can you do about it?
Dust and debris around the wheel encoder are a common cause. Blowing compressed air around the wheel can help. If the problem continues, check whether the mouse is still under warranty, since the encoder is a replaceable part on some mice but not all.
Frequently asked questions
Why does the distance not match my wheel notches?
Browsers report scrolling as events with a pixel distance that depends on your operating system settings and any smooth-scrolling driver. Use the counts to compare directions and spot glitches, not to count physical notches.
Does this work with a trackpad or a free-spinning wheel?
It will register scrolling, but trackpads and free-spinning or high-resolution wheels send different kinds of events, so the glitch counter may flag normal behavior.
How this test works
A direction glitch is logged when one event in the opposite direction appears inside an otherwise steady scroll (for example up, up, down, up within half a second). A real change of direction (up, up, down, down) is not flagged. Free-spinning wheels, trackpads and smooth-scrolling drivers can behave differently from notched wheels.