The space bar, spacebar, blank, or space key,^[1] is a key on a typewriter or alphanumeric keyboard in the form of a horizontal bar in the lowermost row, significantly wider than other keys. Its main purpose is to conveniently enter a space, e.g., between words during typing.

A typical space bar key is large enough so that a thumb from either hand can use it, and is almost always found on the bottom row of standard keyboard layouts.