Mouse scroll test
Log vertical, horizontal, and rapid opposite-direction scroll events in one focused test area.
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How to use it
Place the pointer over the test area and scroll slowly in one direction. Browser scroll events are counted, and direction changes are recorded.
Good to know
Some mice and touchpads send smooth, fractional scroll steps, so counts can differ from physical notches.
Test one direction at a time
Put the pointer over the scroll area and turn the wheel slowly downward for several turns, then repeat upward. The page counts wheel events, shows their direction, and labels an opposite vertical event as a direction jump when it arrives within 150 ms of the prior vertical event. Sideways input is counted separately when horizontal movement is larger than vertical movement.
Look for a repeatable pattern: for example, downward movement that occasionally creates an immediate upward event. Reset between trials so each device or direction has its own count.
What the counts mean
An event is not necessarily one physical wheel notch. Touchpads and smooth-scrolling mice can send fractional or momentum-driven events, and browser or operating-system scrolling settings change their frequency. A direction jump is a useful symptom to compare, not proof that an encoder is faulty. This area prevents normal page scrolling while it has the pointer.
Frequently asked questions
How do I test if my scroll wheel is working?
Scroll slowly down over the test area. Look for repeatable unexpected direction changes. Those events are a clue to compare in another application, not proof of a wheel fault.
Why does my scroll wheel jump up when scrolling down?
Device hardware, smooth scrolling, gestures, settings, and software can affect direction changes. Repeat the movement in another application before drawing a conclusion.
Does this test horizontal scrolling?
Yes. Tilt-wheel and touchpad sideways scrolling is counted separately.