What Is an External Hard Drive?

Definition of External Storage Device

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

An external drive is just a hard drive (HDD) or solid-state drive (SSD) that is connected to a computer on the outside rather than on the inside.

Some external drives draw power over their data cable, which of course comes from the computer itself, while others may require an AC wall connection to derive power on their own.

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.

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 (often in the terabytes), 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.

External hard drive can also be used to provide additional storage to an entire network (though internal hard drives are usually more common in these scenarios). These kinds of network storage devices can be accessed by numerous users at once and often serve as a way for users to share files within a network to avoid emailing or uploading the data online.

Internal Drives Versus External Drives

Internal hard drives are connected directly to the motherboard, whereas external storage devices 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.

Read What Is a Solid State Drive (SSD)? to learn more about the differences between HDDs and SSDs.

Tip: See How to Make an Internal Hard Drive External if you need to "convert" your internal hard drive into an external hard drive.

How to Use an 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.

When it comes to the software side of things, you can use an external hard drive is nearly the exact same way as you would an internal one. The only difference is how you access the drive in your operating system.

Since most computer systems have just one hard drive that serves as the primary, "main" drive, it isn't confusing to jump right in to to the hard drive to save files, copy files from one folder to another, delete the data, etc.

However, an external hard drive appears as a second hard drive and therefore is accessed in a slightly different manner. In Windows, for example, external drives are listed next to the other devices in Windows Explorer and Disk Management.

Common External Hard Drive Tasks

Follow these links if you need help doing any of these tasks with your external storage device: