Scroll Wheel Test
Roll the wheel up, down and sideways inside the box.
Scroll wheel
Ready.
Every test runs inside your browser. Nothing you type, say, show or press is uploaded.
How to use this test
This test counts every scroll step your mouse sends, in each direction, and flags any step that goes the wrong way. When a scroll encoder gets dirty or worn, it often sends a step backwards mid-scroll and the page jumps up while you're scrolling down. Here those jumps are easy to spot.
Point at the test area and roll the wheel down slowly, one notch at a time, then back up. If your wheel tilts sideways or your mouse has a side wheel, try left and right too. Watch the arrows: an orange one reversed direction within 150 ms of the step before it, which a steady scroll shouldn't do.
What the results mean
On most notched mouse wheels each notch sends one step, so ten slow notches should show ten steps in the same direction. Orange arrows in the middle of a steady scroll are the classic sign of a failing encoder. A quick change of direction you make on purpose is marked too, which is why the steady scroll is the part to judge. Touchpads and free-spinning wheels send many small steps instead of one per notch, and that is normal.
Common questions
Why does my page jump up when I scroll down?
The scroll encoder is sending a step in the wrong direction. Dust is a common cause, and a few blasts of compressed air around the wheel sometimes cure it. If the jumps come back, the encoder is worn.
Why do I see lots of steps for one notch?
Touchpads, free-spinning wheels and some mouse drivers send many small scroll events instead of one per notch. With those, check the direction of the steps, not the number.
Can I test horizontal scrolling?
Yes. Tilt the wheel left or right, use a side wheel, or swipe sideways on a touchpad. Left and right steps are counted separately.