payload

Payload is a general term used to describe the part of a system that is being delivered or carried, distinct from the supporting structure or mechanism.

In computing and telecommunications, the payload is the portion of a data unit that carries actual user or application data, as opposed to headers, trailers, or metadata that support routing, addressing, and security. For example, in a network packet, the payload contains the message or file contents, while the header contains addressing and control information. In encryption, the payload may be the plaintext or encrypted data enclosed by protocol wrappers.

In cybersecurity, the term payload also refers to the action carried out by malware after the initial exploit. The delivery mechanism is the exploit or dropper, and the payload is the malware’s functional component, such as data exfiltration, ransomware encryption, or remote control.

In aerospace and spaceflight, the payload is the cargo a launch vehicle or spacecraft is designed to deliver. This includes satellites, scientific instruments, or crew equipment. Payload size and requirements influence vehicle design, mission profile, and insurance. The concept is often discussed alongside payload fraction and the use of a fairing to protect the payload during ascent.

In ground and air transportation, payload capacity denotes the maximum weight of cargo a vehicle can safely carry. It is typically calculated as the vehicle’s gross vehicle weight rating minus its own empty or curb weight. Accurate accounting of payload is essential for performance, handling, and safety.