2.5.2 Pointer Cancellation

When a function fires on the moment a pointer touches a target (the down event), there is no opportunity to cancel an accidental press. By requiring that functions activate on pointer up, or by providing another way to cancel or undo, accidental activations can be prevented.

This matters for users with tremors, motor difficulties, or anyone who may accidentally touch a target while scrolling.

Activate actions on the pointerup or mouseup event rather than pointerdown or mousedown. This is the default browser behaviour for standard buttons and links.

If you must activate on pointerdown, provide an abort or undo mechanism. The user must be able to cancel the action by moving the pointer off the target before releasing, or by a clear undo function.

Avoid attaching actions to touchstart or mousedown events for destructive or hard-to-reverse actions.

• Button that fires its action immediately on mousedown or touchstart with no way to cancel
• Drag-and-drop that triggers a destructive action on pointerdown before the user can abort