Input mask accessibility

Keyboard interaction

Key	Action
`Backspace`	Delete the character before the caret, skipping over literals.
`Delete`	Delete the character after the caret, skipping over literals.

The mask works on your own <input>, so its label and hint stay as you wrote them. Say what’s expected there: a mask isn’t an instruction.
Masks of digits set inputmode="numeric", so phones show a keypad, unless the field sets its own.
Digits of any script are taken, and written 0 to 9.