Tool
Scroll wheel test
Put the pointer in the box and turn the wheel slowly, one way and then the other. This page counts every step the wheel sends, up and down, and flags a wrong-way jump: a step that goes against a steady turn. That jump is what you see as a page that hops up while you scroll down.
Run the test
- Move the pointer into the box.
- Turn the wheel slowly down, about twenty steps, without stopping.
- Turn it slowly up, about twenty steps.
- Read the counts and the wrong-way jumps.
- Repeat at a faster, steady pace.
Turn steadily in one direction at a time. The page only calls a step a wrong-way jump when the turn carries on afterward, so changing direction on purpose is not counted against the wheel.
Read the result
- Wheel events. How many steps reached the browser, split into down and up. A wheel that clicks sends one event for each click you feel.
- Last step. The size of the latest step as the browser reports it, in pixels, lines or pages. The size depends on the browser and the system, so compare it with itself, not with another computer.
- Wrong-way jumps. A single step against a steady turn. A healthy wheel shows none.
A wheel that counts down steps while you turn it up is the fault this test is for.
If the wheel jumps the wrong way
Climb this ladder, smallest step first:
- Repeat it slowly. Run the test twice more at a slow, steady pace, to be sure the jumps come back.
- Change the connection. A fresh battery, another USB port, or the receiver closer to the mouse.
- Try the mouse on another computer. Jumps that follow the mouse are in the mouse.
- Treat it as hardware. A wheel that reports steps it did not make has a fault in its sensor, and no setting repairs that.
When the direction itself is backward
A wheel that always scrolls the opposite way from what you expect is not broken. That is a setting. On a Mac it is Natural scrolling, and how to change the scroll direction on a Mac covers it, including why the mouse and the trackpad change together.
What this page cannot test
The page counts the events a browser receives. It does not measure how far a window moves for each step, which is set by the system, and it cannot tell a tilt of the wheel from a turn. For the buttons, the wheel's click included, use the mouse tester. On a Mac, InputConfig, the free app I make, can give a wheel's tilt a job of its own: the mouse tilt wheel on a Mac has the steps.
Questions
How do I test my mouse scroll wheel?
Put the pointer in the box on this page and turn the wheel slowly one way, then the other. The page counts every step, up and down, and flags any step that went against a steady turn.
Why does my mouse scroll up when I scroll down?
If single steps jump the wrong way in the middle of a steady turn, the wheel's sensor is misreporting, which is a hardware fault. If everything scrolls the opposite way all the time, that is the scroll direction setting, not a fault.
What is a wrong-way jump?
One wheel step in the opposite direction during a steady turn, followed by the turn carrying on. A healthy wheel shows none when you turn it slowly.
Can I test a trackpad or a Magic Mouse here?
Yes. Two-finger scrolling arrives as the same kind of event, in many small steps. The counts climb much faster than with a wheel that clicks.
Related
Free. macOS 14 or later. No account, nothing leaves your Mac. Open source on GitHub.