How to Format an External Hard Drive

If you’ve run into issues with your hard drive, formatting is one of the first steps you should take to troubleshoot it. Formatting allows you to overwrite all data on the hard drive, resetting the file structure and how the drive interacts with the operating system. It can also be used to prep a hard drive for use with another OS. 

In this guide on how to format an external hard drive, we’re going to help you make sure your portable disk works with everything. We’ll show you how to format your hard drive on Windows and macOS and explain the key settings on each OS. 

Before getting to that, though, it’s important to understand what hard drive formatting is. Let’s talk about hard drive formatting, file systems and how formatting doesn’t necessarily erase all data from your hard drive first.

What is Hard Drive Formatting?

Most people associate hard drive formatting with erasing a hard drive. Though that’s true to a degree, it’s not the sole purpose of the process. Instead, formatting is used to get the hard drive to a state in which it can be used by the computer, which requires all written data to be erased from the drive. 


The data isn’t erased completely, but we’ll touch more on that later. Most external hard drives come ready to use on your computer, but in rare cases, you’ll need to format your hard drive. In fact, that’s one of our recommended troubleshooting steps in our how to solve an external hard drive not showing up guide. 

Outside of formatting for initial use, you may need to reformat your hard drive if you encounter errors. In the same way a fresh install of your OS can solve most issues, reformatting your hard drive is a critical step in troubleshooting problems. Just be sure your data is backed up with an online backup service, such as Backblaze, beforehand (read our Backblaze review). 

Before getting into the formatting process, though, it’s important to go over what you’ll be formatting the hard drive with: a file system.

File Systems

File systems are what operating systems use to store data on a storage device. Unfortunately, there isn’t a de facto file system that all hard drives use. The one yours uses largely depends on the drive and the OS you’re using. Because of that, we’re going to go over the most commonly used file systems so you’ll know what’s what.

  • NTFS: NTFS is what Windows uses by default. Like most file systems, it’s restricted once you move outside of Windows. You can read and write on Windows platforms, but macOS and Linux users will only be able to read data from an NTFS-formatted drive. 
  • ExFAT: ExFAT isn’t exclusive to any OS. Windows and macOS can read and write data to it. Though not as prevalent as NTFS, you’ll often find flash drives and external solid-state drives formatted to ExFAT out of the box because multi-platform support and the lack of file size restrictions make it an ideal choice for plug-and-play setups. 
  • FAT32: FAT32 is the older, uglier cousin of ExFAT. Like that file system, it works across Linux, Windows and macOS, and in years past, it was the de facto option for flash drives. It can’t store files larger than 4GB, though, so it has fallen out of favor in recent years. 
  • HFS Plus: Similar to how NTFS is default file system for Windows, HFS Plus is the default file system for macOS. It’s limited on Windows machines, but Apple users will be able to read and write to HFS Plus-formatted drives without issues.

We hope it’s clear now why understanding file systems is important. If you’ve checked out a sideloading guide, such as our Kodi sideloading guide, you probably saw recommendations to format to ExFAT or FAT32. That’s because those file systems work across platforms while NTFS and HFS Plus don’t.

Whichever file system your hard drive shipped with is what you have to use if you don’t want to remove all data from the drive. Alternatively, you could dump the data on your drive to a cloud storage service, such as, format the drive and put your data back on it (read our review).

How to Format an External Hard Drive

Now that we have formatting and file system basics out of the way, it’s time to show you how to format an external hard drive. We’ll show you how to do it on Windows and macOS using the Samsung T5, which is one of the best external hard drives, as you can see in our Samsung T5 review

We chose the T5 because it’s formatted to ExFAT out of the box, meaning it works with Windows and macOS straight away. 

How to Format an External Hard Drive on Windows

Formatting a hard drive on Windows is a simple affair, especially if you leave everything as default. That said, if you want to change settings, you’ll need to know the details of each.

Before getting to those, you have to find the hard drive you want to format by following these steps.


  1. Open File Explorer
  2. Navigate to “my PC”
  3. Right-click the drive you want to format
  4. Click “format” 

Windows will then open the formatting wizard. We’re going to run through each setting in the wizard so you know which settings you need to change. 

  • Capacity: This shows the capacity of the drive. There’s a drop-down, but the full capacity of the drive is usually the only option unless you have partitions set up. If that sounds like gibberish, leave the setting on the default option. 
  • File System: This is the file system you want to format the drive to. There’s a default file system — usually NTFS for internal drives and ExFAT for external — so it’s best to leave that. If you want to change the file system, you can do so here. It’s important to note, though, that internal drives can only be formatted to NTFS. 
  • Allocation Unit Size: The allocation unit size is how large each storage block is on the drive. In almost all cases, leaving the setting on its default is the best option, but you can read up on the math behind it if you’re trying to optimize your drive.
  • Volume Label: This is what you want the drive to be named after it has been formatted. If it’s unnamed, Windows will automatically assign it a name. 
  • Quick Format: The quick format box is toggled by default. That means Windows will delete the file structure of the drive, though the data is still accessible if you use hard drive forensics tools. Doing a full format takes longer, but it’ll overwrite your data and scan for bad sectors.

Though we went over the settings, the best thing to do is probably to leave them on their defaults. Once everything is set, all you need to do is click “start” and wait for the progress bar to fill.

How to Format an External Hard Drive on macOS

Formatting, and dealing with hard drive-related matters in general, is easy in macOS. Unlike Windows, macOS gives you the tools to format, partition, restore and repair your hard drive from a single screen that can be found in your utilities.

To find the screen, follow these steps.


  1. Open Finder
  2. Follow the path /applications/utilities and click “disk utility”
  3. Find your drive in the left-side menu and click it
  4. Click the “erase” tab on the main screen
  5. Select the file system you want to use and give the drive a name

After that, you’re done. macOS doesn’t give you as much control as Windows does, but as we explained, much of that control is irrelevant. The formatting process is simple, with Apple going as far as including step-by-step instruction above the options. 

The only thing you may need to pay attention to is the security options. By default, macOS formats your drive the same way that a quick format does on Windows, meaning the file structure is erased, but the binary data is still there. You can fully erase the data by using the security options. 

How to Fully Erase an External Hard Drive

As mentioned throughout this guide, formatting your hard drive doesn’t erase all the data from it. Binary data needs to be written to the drive at all times, so instead of removing it, your OS deletes the file structure, meaning you can’t access the data on your drive.

For all intents and purposes, your data is erased. You can write new data to the drive, and your OS will show that all the space is available. If you’re disposing of a hard drive, though, someone can still access the data using a forensics tool. Essentially, those tools allow people to bypass the structure of the OS and piece together the files using the binary data. 

As we said, the hard drive always needs to be filled with binary data. The only way to fully erase your data is to overwrite what’s there with new binary data. Though the built-in utilities on Windows and macOS help in parts, a hacker could reverse engineer the process to find the data on the drive. 

There are few options to fully remove data. If you’re getting rid of the drive, a classic solution is to tap it a few times with a hammer to break the disks inside before recycling. If you need to remove data quickly and still want the drive to function, though, you’ll need a separate utility. 

One of the most common is Darik’s Boot and Nuke. It’s an open-source project that rewrites the data on your drive using random processes to ensure it isn’t recoverable. You can boot to DBAN instead of your OS to start the process, which is ideal if you’re recycling or selling your computer.

Final Thoughts

We hope we’ve explained the differences between formatting and erasing an external hard drive.. Formatting isn’t only used to get rid of data on a drive. It’s also used to make a drive compatible with a different OS. The Western Digital My Book, for example, comes formatted to NTFS, but you can reformat it to ExFAT for use with macOS (read our Western Digital My Book review). 

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If you’re looking to add to your external hard drive repertoire, read our external hard drive reviews. There, you’ll find our favorite portable disks, including the SanDisk Extreme Portable SSD (read our SanDisk Extreme Portable review). 

Why do you need to format your drive? Do you have any more questions on the process? Let us know in the comments and, as always, thanks for reading. 

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