Scroll down, then up, over the box: wrong-way events are counted, and you can compare clicks felt with clicks counted.
How to check if a scroll wheel is broken
- With "Test down" on, scroll slowly over the box, about 20 clicks.
- Switch to "Test up" and repeat.
- Watch the chart: plain bars follow the run, red bars marked with a cross went against it.
- To check for skipped clicks, press Clear and turn exactly 20 clicks by feel, slowly. The count should say 20.
Reading the results
- Wrong-way events: short jumps against the rest of a run, and the clearest sign. One may be your finger easing off; two or more points to a dirty or worn encoder.
- Direction doesn't match: if a whole run goes the other way, that isn't a fault. You scrolled the other way, or a setting such as natural scrolling reverses it. Tell the page and carry on.
- Skipped clicks: if you felt 20 clicks and the count is lower, clicks are being missed. Scroll slowly, since fast spins can be merged into fewer events.
- Pause hints: a gap over 2.5 times your usual gap. Usually that's just your finger moving, so it never changes the result by itself.
- Uneven counts: if each direction behaves differently, trust that more than a single number.
Common questions
What is a scroll test?
It records each scroll event from your wheel or touchpad, so you can see the direction and rhythm. This one looks for faults, not scrolling speed.
How do I check if my scroll wheel is broken?
Scroll slowly in one direction and watch for red bars marked with a cross, which mean the wheel reported the opposite direction. If they keep appearing after cleaning, the wheel encoder is probably worn.
Why does my scroll wheel jump up when I scroll down?
Dust in the encoder or wear is the most common cause. Blow compressed air into the gap around the wheel while turning it, then test again.
Why is my scroll sensitivity so high?
That's usually a setting: lines per notch in your system's mouse options, or smooth scrolling in the mouse software. It's not a fault unless the direction is wrong too.
Related tests
- Double Click TestInterval log for every button, with an adjustable limit and a clear fault line.
- Mouse DPI AnalyzerEstimates mouse DPI from a measured distance, averaged over several runs.
- Mouse Polling Rate TestTypical, low, average and high Hz, and it tells you when your browser is the limit.
Privacy
Any page counting is cookie-free; see the privacy page. Results stay in this browser and join your device report.
Technical reference, read 2026-11-01: MDN: WheelEvent.deltaMode.