Scroll Test

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What this tool does

This scroll test lets you check your mouse scroll wheel or trackpad right in your browser: it shows live scroll direction, delta X/Y values, delta mode, total distance scrolled, scroll speed, and a full event log, with automatic detection of wheel chatter, a common sign of a worn-out or failing mouse scroll wheel.

How It Works

Every scroll is captured as a native browser wheel event, which reports deltaX and deltaY (how far you scrolled on each axis), and deltaMode (whether that distance is measured in pixels, lines, or pages). The direction is whichever axis has the larger absolute delta: a bigger deltaY means up or down, a bigger deltaX means left or right. Total distance sums the absolute delta of every event, and scroll speed divides that total by the time elapsed between the first and most recent event. Wheel chatter detection compares the timestamps of consecutive same-direction events, since a real mechanical wheel encoder cannot physically re-trigger within a few milliseconds, any pair that close together is flagged as a likely double-fire rather than two intentional scrolls.

Problems it solves

• Diagnosing an erratic or double-scrolling mouse wheel before deciding whether to replace it.
• Confirming that all four scroll directions, including horizontal tilt, register correctly.
• Checking exactly what delta values and delta mode your specific mouse or trackpad reports.
• Testing a new or secondhand mouse's scroll wheel before relying on it for daily use.

Frequently asked questions