The easiest way to add storage to your Mac is to buy an external hard drive. Once you have it, your first task is to pick a suitable file system for that drive depending on your intended usage.
With the Disk Utility app, you can easily format the drive, give it a label, or even partition it and create multiple volumes. Let’s look at the best file system formats to use for your Mac's external drive.
How to Format Your Drive With Disk Utility
Once you’ve bought a new external storage drive, connect it to your Mac. It’ll likely be already formatted, either for Windows (using NTFS) or for maximum compatibility (using FAT32). For a Mac user, neither of these file systems is desirable.
Open the Disk Utility app. In the left panel, you’ll see the listing of internal and external drives separately. Now choose View > Show All Devices to see the storage device at the top level, then the container, and finally any volumes that are in the container.
In the sidebar, select the external storage device. Be sure to choose the device, not the volume or volumes it contains. In the toolbar, click Erase. Type in the disk name you want, then select your preferred option for both Format and Partition Scheme.
Note: You’ll lose all the data in the external drive, make sure to back it up.
If you run into issues while formatting, read our guide on how to unlock your Mac external drive.
Here are some questions that you should evaluate before formatting the disk:
- Do you wish to use the external drive on other Macs? If yes, then find out the OS version and model.
- Is the external drive for Time Machine backup or not?
- Do you want to share the drive with a Windows machine? If yes, do you have a backup plan of that drive in case the data gets corrupted?
Mac File Systems Explained
Disk Utility allows you to choose from a variety of file system formats. Let’s take a detailed look at each of them, what they’re used for, and which you should pick for your external drive.
Apple File System (APFS)
APFS is Apple’s modern file system, first launched in early 2017 for iOS devices. The experimental support of APFS was first seen in macOS Sierra. In High Sierra, SSD boot drives were converted to APFS upon installation. As of macOS Mojave, fusion drives and HDDs were also upgraded to APFS.
The current Apple File System documentation highlights many improvements over HFS+. It makes common operations such as copying files and folders instantaneous. You can also manage free space on the drives efficiently, copy-on-write metadata scheme to improve performance, thereby reducing chances of data corruption, and increased focus on encryption.
When to Use APFS:
- If speed and convenience are your top priorities and cost is not an issue. An external SSD gives you the best performance over APFS, provided you don’t need to use the drive with other pre-Sierra Macs.
- On macOS Big Sur, Apple lets you format an external drive and choose APFS for Time Machine. However, you won’t be asked this option for the already formatted HFS+ disk.
- Time Machine backups to APFS are impressive when compared to HFS+. It’s fast, consumes less space, which means more room for backups, has greater resistance to data corruption, and copies cloned or sparse files efficiently.
- Time Machine volumes formatted as APFS will only work with Macs running Big Sur or later. If you connect that disk to Catalina, Time Machine won’t recognize it.
- You can only access drives formatted with APFS on Windows through third-party apps. Here are some of the best apps that read-write APFS on Windows.
Mac OS Extended (HFS+)
Mac OS Extended, also known as HFS+ (Hierarchical File System Plus), was the main file system used for Mac system storage from 1998 until APFS launched in 2017. If you bought a Mac between those dates, it shipped with macOS (or OS X, as it was known) installed on an HFS+ volume.
When to Use HFS+:
- If you have older Macs (pre–2016), particularly those too old to update to a recent version of macOS, choosing HFS+ will enable you to use your external drive with those machines.
- For Time Machine backups, use MacOS Extended (Journaled) if it’s a mechanical hard drive or if you’re using macOS Catalina or earlier. Even if you’re using SSD as a Time Machine drive, it’s not compatible with APFS.
- You can only access drives formatted with HFS+ on Windows through third-party apps. Manufacturers like Seagate lets you read and write data interchangeably on Windows and Mac without formatting the external drive.
Extended File Allocation Table (exFAT)
This was designed by Microsoft to provide similar compatibility to FAT32 without the pesky limitations. exFAT is the preferred file format for flash storage drives that you share between Windows and Mac. exFAT has no realistic file or partition size limits. It also doesn't require complicated ACLs and file attribution system like NTFS.
When to Use exFAT:
- Both Mac and Windows offer full read and write support for exFAT. If you frequently share files between your Windows-using friends and family, it’s the ideal format.
- As highlighted from this file system functionality comparison from Microsoft, exFAT does not support journaling, nor does it have built-in encryption. You may lose data in the event of a crash.
MS-DOS (FAT)
Apple also includes support for FAT32, labeled as MS-DOS (FAT) in Disk Utility. You should generally avoid using FAT32 for any purpose unless you’re dealing with an old computer or device.
When to Use MS-DOS (FAT):
- Flash drives you purchase will often come formatted with FAT32 for maximum compatibility with old computers (likely running Windows XP) and even games consoles.
- Individual files on a FAT32 drive can’t be over 4GB in size. Also, the partition must not exceed 8TB. exFAT is almost always a better choice.
Support for NTFS Drives
NTFS, which replaced FAT32 with the arrival of Windows XP, is still the dominant Windows file system. FAT32 had many serious limitations, including a maximum file size of 4GB and a partition size of 8TB. This makes it unsuitable for most modern purposes.
macOS can read NTFS file systems natively, but it is unable to write to them. To enable write access, you should use a third-party utility like Paragon NTFS for Mac or Tuxera NTFS for Mac. These utilities have been tested far more thoroughly, and allow you to write to your existing NTFS volumes and format new drives to NTFS.
Using an External Hard Drive for Time Machine Backups
Ideally, the best file format is the one that covers your needs across all the platforms you use. For the best Time Machine compatibility, reformat your device with the GUID partition map scheme and HFS+ or APFS file format.
The release of Big Sur with APFS compatibility for external drives will change the way we store or take backups. And as SSDs have become cheaper, we recommend using one of them for Time Machine and data backups.