Observe mouse buttons, movement and wheel events
Use a focused area to see the mouse events the page actually receives.
Try different interactions
Start the Mouse test, then move, press/release buttons, drag, double-click and scroll in the area. The display reports button, buttons bitmask, click detail, local/viewport position, movement and wheel deltas. Context menu is suppressed only inside the active mouse test so secondary clicks can be inspected.
Read the raw values
Common button indices 0 primary, 1 auxiliary, 2 secondary, 3 back and 4 forward have labels. Other indices remain explicitly unmapped. buttons is a bitmask: 1 primary, 2 secondary, 4 auxiliary, 8 back, 16 forward. Dragging means a movement event reports a nonzero buttons mask. Wheel direction is derived only from delta sign; deltaMode 0/1/2 denotes pixels/lines/pages.
Limits
Browser/OS acceleration, event coalescing and navigation shortcuts can affect observations. This is not a hardware polling-rate or latency certificate, and missing events alone cannot diagnose a device fault. Focus loss clears live button state and pauses logging; retained events remain until reset.