About this test
A dirty or worn scroll encoder often sends a step in the opposite direction, which makes pages jitter or jump while scrolling. The scroll wheel test records every wheel event, counts steps up, down and sideways, and flags single reversed events inside a steady scroll so you can see the fault clearly.
How to use this test
- Point at the test area and scroll slowly downward for 20 steps.
- Then scroll upward for 20 steps.
- Red marks show wrong-direction events. More than one or two suggests a faulty encoder.
Frequently asked questions
What causes scroll wheel jumping?
Dust or wear in the mechanical encoder. Compressed air sometimes helps; otherwise the encoder needs replacing.
Why does one step scroll a different amount?
That is the delta value, set by your operating system's scroll settings and the mouse driver.