In cargo transport, payload is the valuable contents of the vehicle.

Similarly, in military aircraft, payload is the carrying capacity of an aircraft, whether as cargo, munitions, or external fuel, although internal fuel is usually not included.

See also Tsiolkovsky rocket equation.

In communications and information science, the payload or mission bit stream is the data, such as a data field, block, or stream, being processed or transported — the part that represents user information and user overhead information. It may include user-requested additional information, such as network management and accounting information. Note that the payload does not include system overhead information for the processing or transportation system.

In computer virus jargon, the payload of a virus or worm is any action it is programmed to take other than merely spreading itself. The term is used for all intended functions, whether they actually work or not.

Based on text from Federal Standard 1037C.