Network-attached storage (NAS) is a device consisting of one or more hard drives, an Ethernet connection, and an embedded operating system rather than a full-featured network operating system. The NAS device connects to the network, allowing users on the network to access and share files, stream media, and back up data to a central location. NAS devices that support multiple hard drives can provide RAID-level data protection.

NAS is a client/server design. A single hardware device, often called the NAS head, acts as the interface between the NAS and the network clients. Clients always connect to the NAS head, not the individual storage devices. A NAS device requires no monitor, keyboard, or mouse.

NAS systems provide easy administration. They often include built-in features, such as disk space quotas, secure authentication, and automatic sending of email alerts if an error is detected in the equipment.