Guide
What NAS is, and when it's worth having one at home.
A NAS isn't just 'a more expensive hard drive.' It's a device with its own operating system that makes your files available to your whole network, without depending on a specific computer being turned on.
The key difference from an external drive
An external hard drive connects directly to a single computer over USB — only that computer can access the files, and only while the drive is physically connected. A NAS (Network Attached Storage) connects to the router over a network cable, not to a specific machine, and runs its own operating system independently. Any device on the same network — laptops, phones, tablets, smart TVs — can access the NAS's files at the same time, with no computer needing to be turned on.
The three most common home uses
Centralized media library: you keep movies, music and photos in one place, accessible from the smart TV, phone or any computer in the house, without duplicating files across devices. Automatic backup of multiple devices: you set up every laptop and computer in the family to automatically back up to the NAS over the local network, without relying on someone remembering to plug in an external drive. Simultaneous multi-user access: several people in the house (or team, in a work context) can save and read files at the same time, something an external drive connected to a single computer doesn't practically allow.
When a NAS isn't necessary
If you only need to back up one personal computer, an external drive or a cloud service (check the cloud storage cost comparison) is usually simpler, cheaper and enough. A NAS has a steeper initial setup curve and a higher entry cost (the device plus the drives), so it makes more sense when the real problem is sharing files across several people or devices, not just backing up one.
RAID inside a NAS: redundancy, not a backup replacement
Most home NAS units with two or more drive bays let you configure RAID (for example, RAID 1 with two disks) to protect against a single disk's failure. It's important to remember this protects against hardware failure, not against accidental deletion, ransomware, or theft of the whole device — for that you still need a real backup outside the NAS. See which RAID level makes sense in the RAID 0, 1 and 5 guide.
Verifiable sources
The technical definition of NAS, its most common home uses, and how it differs from a direct external drive are documented by TechTarget, a standard reference source for storage infrastructure.