What Is an External Hard Drive?

Definition of External Drive

Photo of a blue, WD My Passport Ultra 2TB portable external USB 3.0 hard drive
Western Digital 2TB USB 3.0 External Hard Drive. © Western Digital

What Is an External Drive?

An external drive is just a hard drive or SSD that is connected to a computer on the outside rather than on the inside.

Some external drives draw power over their data cable, while others may require an AC wall connection.

One way to think of an external hard drive is as if it were a regular, internal hard drive that has been removed, covered in its own protective casing, and plugged into the outside of your computer.

Internal hard drives can even be converted into external hard drives via what's called a hard drive enclosure.

External hard drives come in varying storage capacities, but they all connect to a computer either by USB, FireWire, eSATA, or wirelessly.

External hard drives are sometimes called portable hard drives. A flash drive is one common, and very portable, type of external hard drive.

Using an external hard drive is as easy as plugging one end of the data cable into the drive as well as to the matching end on the computer, like the USB port in the case of USB-based external drives. If a power cable is required, it will need to be plugged into a wall outlet.

Normally, on most computers, it takes just a few moments before the contents of the external drive will appear on-screen, at which point you can begin moving files to and from the drive.

Why Would You Use an External Drive?

External hard drives are portable, easy to use, and can provide a large amount of storage whenever you need it.

You can store the actual device any place you like, and carry a large number of files with you wherever you go. 

Another advantage of owning an external drive is that you can move them from computer to computer, making them great for sharing large files.

Because of their usually large storage capacities, external hard drives are often used to store backed up files.

It's common to use a backup program to back up things like a music, video, or picture collection to an external drive for safe keeping, separate from the originals in case they're accidentally changed or deleted.

Even if not used for backup purposes, external hard drives provide an easy way to expand your existing storage without having to open up your computer, which is especially difficult if using a laptop.

Internal Drives Versus External Drives

Internal hard drives are connected directly to the motherboard, whereas external drives first run through the outside of the computer case, and then directly to the motherboard.

Operating systems and software installation files are generally installed to internal drives, while external hard drives are used for non-system files, like photos, videos, documents, and files of those types.

Internal hard drives draw power from the power supply inside a computer. External hard drives are powered either through their data cable or via dedicated AC power.

Data can be compromised much easier if it's stored on an external hard drive because they're generally located on a desk or table, making them very easy to pick up and steal. This is different than an internal hard drive where the entire computer has to be taken, or the hard drive removed from the inside, before someone can have physical access to your files.

External hard drives are also generally moved around more than internal ones, causing them to fail more easily due to mechanical damage. SSD based drives, like flash drives, are less prone to this sort of damage.

Common External Hard Drive Tasks