AD is a screesaver file native to After Dark software developed by Berkeley Systems. AD file stores static images and animations that are displayed on the screen after a defined period of user inactivity.

AD screeensavers were popular in the 1990s and the format is no longer supported by the developers. Users can still purchas a license for individual screensaver file or package of such files on developers website. The most popular screensaver, Flying Toasters, is available only for Mac operating systems.