You’ve got your drive ready to use for your Time Machine backup. And now you’ve a choice to make. APFS or Mac OS Extended for Time Machine.
What are the things to keep in mind when picking one or the other.
For Time Machine APFS VS Mac OS Extended Compared
For Modern Macs running Mac OS Big Sur 11.0 or later the APFS file system is the best choice for a Mac Time Machine backup.
For Macs running Mac OS Catalina 10.15 or an older Mac OS X. Those older OS versions do not support APFS for back up with Time Machine. On those Macs, Mac OS Extended (HFS+) is the only choice.
Read on to know more.
The Time Machine APFS Mac OS Extended Question
For a new Mac that runs Mac OS Big Sur, Monterey and later. Then quite honestly you can pick either file system format for Time Machine.
Your Mac’s version of Time machine will quite happily use the APFS format or Mac OS Extended.
When you’d pick one file system format over the other then comes down to how much you have to backup. Intersected with your budget for an external drive and how fast you need to backup.
On older Mac’s running Mac OS Catalina, Mojave, High Sierra or Sierra.
The choice is simple.
It’s Mac OS Extended Journaled. Because although Mac’s since Mac OS 10.13 High Sierra support an APFS volume on an external drive. They don’t support a Time Machine backup to an APFS volume.
Let’s dive into some of the subtleties on why you’d pick APFS or Mac OS Extended.
When Would You Use APFS For Time Machine Over Extended Journaled?
Apple themselves suggest that an APFS formatted drive is the best format choice for Time machine. And for newer Mac’s with APFS as the default file system that’s true.
But there are a few things to be aware of.
APFS (Apple File System), created by Apple Inc. Was made to take advantage of the faster speed of an SSD drive or a flash drive.
APFS is created for those drives and is optimized for them.
So, APFS is the clear choice when you have an external SSD (Solid State Drive) to back up to.
Picking APFS On SSD’s Size And Speed Of Backup?
But if your Mac has 1TB or more on it. And those drives are pretty full. Then you would be looking at 1TB or more of data to backup. Plus, your Time Machine backup drive will need room for you to grow your backup into.
You’ll want an APFS backup drive large enough to hold what you’re backing up. With room to grow. Say, 50% extra or more free space on your drive.
In this setup you’d be looking for an SSD drive of 2TB or more. That’s quite a costly prospect. When you could get yourself an 2TB external hard drive at a fraction of the cost of the SSD.
If money is no object. Or you’ve much less to backup. Then an SSD drive would be an excellent choice.
And if the speed of backup and restore is important to you. Then that’s another good reason to pick an external SSD APFS drive to back up to.
And because new Macs have internal SSD drives on them. And those internal drives run APFS as the default file system. You’d be backing up and restoring APFS to APFS getting yourself the fastest possible speed.
Versus Mac OS Extended For Time Machine Instead Of APFS
The Mac OS Extended format (HFS+) was created at a time when mechanical drives were the only option you had. Back in the late 90’s through 2000’s it was the only choice for any drive on a Mac.
FYI, Mechanical drives are also known as a hard drive or hard disk. Because they have moving parts inside.
And this means that Mac OS Extended is optimized for, and made for hard drives.
Mac OS Extended is the file system format to pick for a backup disk drive for earlier Mac OSX releases. Like Mac OS X Catalina, Mojave or Sierra.
For an older Mac with a hard drive inside, running earlier operating system releases. Mac OS Extended is the only choice. Because those Macs do not support an APFS backup disk drive. Mac OS Extended is the default file system on those Macs.
Plus running Mac OS Extended when you’re backing up Time Machine to a hard drive causes less wear and tear on the drive.
Because APFS stores file metadata with the file rather than in a fixed location like Mac OS Extended does. 
And this means APFS causes extra seeks and hardware movement on a hard disk drive.
Though as a normal Mac user you’re unlikely to have a problem with this issue. Particularly on a backup disk. Because most of the time you’re writing your data out to the drive in a Time Machine backup.
And only occasionally restoring from a backup disk.
But if you’ve partitioned up your hard disk. And maybe have one partition dedicated to your backup. Another partition to store your files and work on those files directly from your hard drive. You’ll want to keep this in mind.
If you’re driving your external hard drive hard you may want to consider staying with Mac OS Extended.
Some Advantages Of APFS For A Safe Time Machine Backup
Apple Inc. built APFS to be more secure than Mac OS Extended. And a more secure file system format keeps your Time Machine backups safer.
APFS offers better security, file encryption and data recovery features than Mac OS Extended.
What does that mean?
A sudden power failure or disconnection will trigger the APFS drive to roll back. And better protect your important files.
Compared To Mac OS Extended For A Safe Time Machine Backup
Mac OS Extended Journaled is called an Extended Journaled file system. Because it’s a journaled file system.
This means it keeps track of changes made to the file system. Keeping your files safer.
You also have a drive encryption option should you want to encrypt your drive.
As the older of the two file systems, you have the assurance that the file system has been around for years. Older Mac’s internal drives used Mac OS Extended. And it was used extensively on external drives.
Time Machine Offering To Format Your Drive Some Things To Know
On modern Macs. Since MacOS Big Sur. When you connect up an external drive that’s not formatted for Mac to use with Time Machine. Your Mac’s Time Machine will offer to format it for you.
The default formatting will be APFS. With the drive as one Time Machine volume container and no partitions.
If you’re only using your drive for Time Machine that may be fine for you.
But, if you’d prefer to have your drive Mac OS Extended formatted. Or have partitions on your drive. Say, a partition to back up to and another partition to store certain files. Then refuse that offer from your Mac.
And use Disk Utility on your Mac to format your drive as you want.
To use Disk Utility to format a NTFS drive or ExFAT formatted drive as APFS. You’ll need to format to Mac OS Extended with a GUID Partition Map first.
Then follow that formatting as APFS with a GUID Partition map.
After that you can set up your partitions. And the format for each of the partitions you want after that initial formatting.
Using A Mac OS Extended Time Machine Backup Drive From An Old Mac To A New APFS Mac
When you’re looking to build your new APFS based Mac from a Time Machine backup on a Mac OS Extended external drive. The software you use to do that is Migration Assistant.
Because you can’t generally migrate Time Machine backups from one Mac to another. Time Machine backups are keyed to the Mac they are taken on. And Migration Assistant on a Mac gets you round that restriction. And works very well.
If you connect up your old Mac’s Mac OS Extended based Time Machine backup, to Time Machine on your new APFS Mac. Time Machine will want to reformat your older drive wiping off the old backup on there.
A backup you may want to keep.
If you want to keep the backup drive from your old Mac. Then get yourself a new drive. Decide what file system format you want for that Time Machine drive for your new Mac. And start your new Mac backups from fresh.
Connecting An APFS Drive To Time Machine Vs Mac OS Extended
Once you’ve formatted your external drive how you want. You won’t see any difference in how you connect either file format in System Preferences to Time Machine.
All the commands are exactly the same. And once you’ve got either file system format set up, you’ll notice little difference when you back up to the drive.
Except speed differences between a hard drive and SSD. And some subtle differences between APFS and Mac OS Extended.
And now you know what to consider when you’re thinking APFS or Mac OS Extended for your Time Machine backup.
The age of your Mac and the operating system it runs are important factors. And whether it’s an external SSD or external hard drive comes into the mix as well.
While you here why not take a look at the other articles around different formats for Mac on the site.
About Paul Gregory
I’ve been a system administrator for various corporates for 15 years. And as admin I’ve helped many with their Mac’s and there many Apple devices.
I’m excited by watching users, armed with a little knowledge take control of their Mac’s and their files. And why not?
When I’m not at work or working on the site I like to chill with few beers. And watch a bit of car racing. From Formula 1 to stock car racing. The competition is my thing.