What the Mouse Scroll Test Measures
The browser reports wheel delta values and direction. The test counts upward and downward events and can compare them against an intended direction selected by you.
Trackpads and smooth-scrolling software can generate a stream of small wheel events, so compare similar input devices and movement styles.
How to Use the Mouse Scroll Test
- 1Choose Up Only or Down Only for a controlled test; use Free mode to inspect general input.
- 2Move the wheel slowly in the chosen direction inside the area.
- 3Check reverse events and the recent delta chart.
- 4Repeat several runs and try another browser if the direction changes unexpectedly.
How to Interpret the Result
A reverse event is meaningful only when your intended direction is known. A direction change in Free mode is normal behavior, not a failure.
Repeated reversals in a controlled direction may be consistent with a wheel encoder or software issue; one event cannot identify the cause.
Controlled Direction vs Free Scrolling
Choose a single intended direction when you want a reverse-event count. In Up Only mode, a downward wheel event is opposite the stated intention; in Down Only mode, an upward event is opposite. The reverse rate divides those opposite events by all observed wheel events in that run.
Free mode is useful for seeing that the wheel reports both directions, but it should not label intentional changes as a failure. If you use a trackpad, its smooth gesture events and momentum may continue after your fingers stop, so compare results with the input device in mind.
Browser Limitations
Wheel deltas are browser events, not physical wheel notches. Trackpad gestures, browser normalization and scrolling software can change their magnitude. This test cannot inspect the mouse encoder electrically.