Mouse wheel test
Scroll inside the box. Each step lights an arrow and draws a bar, so a step in the wrong direction stands out.
Mouse wheel test workspace
How to use
4 short steps.
Scroll down steadily
Roll the wheel toward you for a few seconds at an even pace. Every bar should sit below the line.
Scroll up the same way
Roll the wheel away from you. Every bar should now sit above the line and the Up arrow should flash on each step.
Try fast and slow passes
Some wheels only skip at one speed. Repeat each direction quickly, then slowly, and watch the suspected skips count.
Tilt the wheel if it can
Push the wheel left and right. The side arrows flash when horizontal scrolling arrives.
What the result means
Match what you see to one of these.
If every bar is on the same side, the wheel is fine
If a steady run draws bars only above or only below the line, every step went the right way and nothing was missed.
If a bar appears on the wrong side, the wheel skipped
If one bar lands on the opposite side during a steady run, the encoder sent a step backwards. The suspected skips counter records it.
If nothing happens, the wheel is not reaching the browser
If the event count stays at zero while you scroll, the wheel encoder, cable, or a driver setting is stopping the signal.
Troubleshooting
If the test fails, try these in order.
Check the scroll direction setting
Windows: Settings, Bluetooth and devices, Mouse, Scrolling direction. macOS: System Settings, Mouse, Natural scrolling. Change it, then scroll here again.
Clean the wheel encoder
Unplug the mouse and blow compressed air into the gap around the wheel. Dust on the encoder causes skips. Scroll a steady run again.
Update or reinstall the mouse driver
Vendor software can add smoothing or acceleration that reorders steps. Update it or set scrolling to default, then retest.
Try another port or computer
Use a different USB port, then another computer. If the skips follow the mouse, the encoder is worn and the mouse needs repair or replacement.
What this test can't tell you
Where a browser check stops.
- The browser reports wheel deltas in pixels, lines, or pages after the operating system has processed them, so the numbers are not physical notches.
- A free-spinning wheel or a trackpad with momentum keeps sending steps after you stop, which looks different from a notched wheel.
FAQ
Common questions about this test.
How do I know if my mouse wheel is broken?
Scroll steadily in one direction on this page. A working wheel draws every bar on the same side of the line. Bars on the wrong side, missing steps, or a count that stops rising point to a worn encoder.
My mouse wheel is not scrolling. What can I do?
Check the scroll settings in your operating system, clean the wheel with compressed air, update the driver, and try another USB port. Then scroll here again to confirm the fix.
How do I calibrate my mouse wheel?
There is no browser calibration. Set lines per notch and scroll direction in your operating system, and smoothing in your mouse app. This page shows the result of those settings.
What is Ctrl plus scroll?
Holding Ctrl while scrolling zooms most pages and apps. Inside the box on this page it counts as a normal step and does not zoom.