Space bar

A computer keyboard, Space Bar is on the bottom center of the keyboard

The space bar, spacebar, or space key, 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 QWERTY or Dvorak keyboard layouts. Originally (on early typewriters dating back to the late 19th century) the "bar" was literally that, a metal bar running across the full width of the keyboard (or even wider, and even surrounding it) that triggered the carriage advance without also firing any of the typebars towards the platen. Later examples gradually shrank and developed into their current more ergonomic form as a wide, centrally located but otherwise apparently normal "key", as typewriter (and computer) keyboards began to incorporate additional function keys and were more deliberately "styled". Although it varies by machine, language, and even operating system, the space bar usually lies between the Alt keys (or Command keys on Macintosh keyboards) and below the letter keys: C, V, B, N and M.

Some early typewriter and particularly computer keyboards used a different method of inserting spaces, typically a smaller, less distinct "space" key which was also often set in a less central position, e.g. the Hansen Writing Ball, Hammond typewriters or the Sinclair ZX and Jupiter Ace ranges. However these were also usually just one part of similarly idiosyncratic full keyboard layouts, designed more to cope with particular technical requirements or limitations than with any sense of user friendliness and as such met with limited success, sometimes being dropped even on later models in the same line (e.g. Sinclair Spectrum 128k and "Plus" lines, which adopted more "normally styled" keyboards with plastic keytops and a wide, central spacebar in place of the earlier rubber "chiclet" keys and small, offset space key).

Depending on the operating system, the space bar used with a modifier key such as the control key may have functions such as resizing or closing the current window, half-spacing, or even backspacing. On web browsers, the space bar usually allows the user to scroll down or to scroll up when the space bar is used with the shift key.

In many programs for playback of linear media, the space bar is used for pausing and resuming playback, or for manually advancing through text.