Scroll wheel test

A mouse wheel test: scroll steadily in one direction. Every wheel step is shown; steps that jump the wrong way show up in red.

Scroll here

Scroll steadily down for a few seconds, then steadily up. The page won’t move while you’re in this box.

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Each bar is one wheel step: blue down, green up, red a jump in the wrong direction.

Scroll a bit more for a result.

runs locally in your browser · nothing is recorded or uploaded

How to test your scroll wheel

  1. Put your pointer in the box. The page won’t scroll while you’re inside it.
  2. Scroll down slowly and steadily for 5–10 seconds, then up for 5–10 seconds.
  3. Each wheel notch adds a bar: blue for down, green for up. A red bar is a step in the wrong direction in the middle of a scroll.

What the results mean

ResultMeaning
No red barsYour wheel reads every step correctly.
Occasional red barsA dusty encoder. Compressed air often fixes it.
Red bars on most scrollsA worn encoder. Cleaning may help briefly; replacing is the lasting fix.
Nothing registersThe wheel isn’t sending scroll events: try another port or check the mouse software.

Test the buttons as well with the mouse test.

FAQ

Why does my scroll wheel jump up when I scroll down?

The wheel's encoder, a small sensor that counts each notch, gets dirty or worn and occasionally reads a step in the wrong direction. The page then jumps back while you scroll. The scroll test counts these reversed steps.

How do I fix a skipping scroll wheel?

Blow compressed air around the wheel while turning it, in both directions. If that doesn't help, the encoder needs cleaning with contact cleaner or replacing, or it's time for a new mouse. Check the warranty first.

Does this test work with trackpads?

It works, but trackpads send smooth, tiny scroll steps and inertia, so a reversal at the end of a swipe can look like a jump. The test is most useful for mouse wheels.

More tests

Keyboard test Press every key and see which ones work, stick or ghost. Mouse test Check every button, the scroll wheel and double-click faults. CPS test How many clicks per second can you do? 1, 5, 10, 30 or 60 seconds. Double click test Find out if your mouse registers one click as two. Polling rate test Measure your mouse's polling rate in Hz. Dead pixel test Fill your screen with solid colors to find dead and stuck pixels.