An all-in-one desktop computer integrates the system's internal components into the same case as the display, thus occupying a smaller footprint than desktops that incorporate a tower.

The All in One form factor was popular during the early 1980s for computers intended for professional use such as the Kaypro II, Osborne 1, TRS-80 Model II and Compaq Portable. Many manufacturers of home computers like Commodore and Atari included the computer's motherboard into the same enclosure as the keyboard; these systems were most often connected to a television set for display. Apple has manufactured several popular examples of all-in-one computers, such as the original Macintosh of the mid-1980s and the iMac of the late 1990s and 2000s. Some all-in-one desktops, such as the iMac G4, have used laptop components in order to reduce the size of the system case. By the mid 2000s, many all-in-one designs have used flat panel displays, and later models have incorporated touchscreen displays, allowing them to be used similarly to a mobile tablet.

Like laptops, some all-in-one desktop computers are characterized by an inability to customize or upgrade internal components, as the systems' cases do not provide convenient access to upgradable components, and faults in certain aspects of the hardware may require the entire computer to be replaced, regardless of the health of its remaining components. There have been exceptions to this; the monitor portion of HP's Z1 workstation can be angled flat, and opened like a vehicle hood for access to internal hardware.