Which format to use for an external drive on a Mac

One question decides it. What else has to read this drive. For a Mac alone the answer is APFS. Where Windows also has to write, exFAT is the only shared option and it carries a real risk. For a camera or a console the device dictates the format and you have no choice to make.

Every new external drive arrives formatted for the widest possible audience, which is rarely the right choice for you specifically. Here is how to pick, by what the drive is actually for.

Pick your row

Read the second column, then stop. The comparison between the two Apple formats has its own answer in what actually changed between APFS and Mac OS Extended. This page is about which one your drive should be.

A Mac and nothing else

Apple File System, unless the drive spins.

It is journaled, so an interrupted write survives. It encrypts as a property of the volume rather than through a layer added on top. It shares free space between volumes on the same drive, so you can carve a backup volume and a working volume out of one disk without deciding their sizes in advance.

The exception is a mechanical drive. APFS scatters metadata alongside data and writes changes to new blocks, both of which cost a moving head real time. On a platter, Mac OS Extended still reads directories faster. HFS Plus is the same format under its older name.

One condition on that. From macOS 28, Mac OS Extended is supported only where the volume is not encrypted. If a hard disk has to be both Mac OS Extended and encrypted, that combination stops mounting. Pick one.

A Time Machine drive

APFS, which macOS will offer to do for you.

Select a drive that is not already APFS and Time Machine offers to erase and reformat it on the spot, because APFS is what Apple wants a backup disk to be.

Say yes with two things in mind.

The whole APFS volume gets reserved for backups. To keep other files on the same physical drive, make a second volume in Disk Utility and the two share the space.

An existing Mac OS Extended backup drive is left alone. Apple still supports it. There is no conversion. Moving that drive to APFS means erasing the history and starting the chain again.

A Mac and a Windows PC

exFAT, with conditions attached.

It is the only format both systems read and write without buying anything. That is the entire case for it. It is enough on its own for a drive that carries files between two machines.

What it is not is a safe home for the only copy of something. The reasons are in the next section.

The alternative nobody mentions is to skip the shared format entirely. Format for whichever machine does the real work, then buy a driver for the other one. On a Mac that means reading and writing NTFS through third party software. It costs money and it removes the risk exFAT brings.

The exFAT problem

Every guide recommends exFAT for cross platform use. Very few say what you are accepting.

It has no journal. APFS, Mac OS Extended and NTFS all keep a log of changes before making them, so an interrupted write can be unwound. exFAT keeps nothing. Pull the cable during a write. Lose power. Let a laptop sleep mid transfer. The damage is not limited to the file in flight. The volume itself can go.

It drops Mac metadata. Extended attributes, resource forks and Unix permissions have nowhere to live on exFAT. Copy a folder out and back and some of that is simply gone. For anything where file integrity matters this is not a small detail.

The two systems do not always agree. A volume created by Windows and one created by macOS are not always interchangeable. A drive that mounts on one can refuse on the other.

The rule that follows from all three. Use exFAT for moving things, never for keeping them. If a drive is the only place a file lives, it should not be exFAT.

A camera or an SD card

The card size decides this and the camera enforces it.

The SD Association designates exFAT as the standard for SDXC cards, which is everything from 64GB upward. Cards at 32GB and below are SDHC and ship as FAT32.

The reason the standard moved is the 4GB file size ceiling on FAT32. A ten minute clip at a modern bitrate passes that comfortably, so a FAT32 card either splits the recording or stops.

Format in the camera rather than on the Mac. The camera writes its own folder structure during the format and expects to find it later. Use the Mac only to change the file system or to recover a card that has errored, then format again in the camera before shooting.

A PlayStation or an Xbox

exFAT, because the console does not offer much else.

PlayStation accepts exFAT or FAT32 and nothing else. NTFS is refused outright. So is APFS. Xbox takes exFAT for extended storage in the same way.

Between the two allowed options exFAT wins on the same 4GB argument. Game installs and captured video both pass it.

The simplest route is to let the console format the drive from its own settings menu. It knows what it wants.

A drive somebody else formatted

Leave it as it is until you have copied what you need off it.

A Mac mounts an NTFS drive and reads it perfectly well. It cannot write to it without third party software, which is what makes people reach for Disk Utility.

Reformatting is not a repair. It erases everything on the drive. If the reason you want to write to that drive is that it holds files somebody sent you, copy them to the Mac first and decide about the format afterwards. Why the Mac refuses to write to it in the first place has the full order of operations.

What choosing a format does not do

Two expectations get attached to this decision that it cannot carry.

A format is not a backup. APFS on an external drive holds one copy of your files in one place, exactly as exFAT would. The journal protects the volume from an interrupted write. It does nothing about a drive that dies, a drive that walks off or a folder deleted by mistake.

A format is not speed. On a modern connection the bottleneck is the cable and the drive, not the file system. The differences that matter here are about what survives an accident and what other machines can read, not about how fast a copy finishes.

Where the format does earn its place is the boring cases. A cable pulled at the wrong moment. A Mac that slept with the drive mounted. A machine at the other end that has never heard of the format you chose. Those are the situations the table above is answering.

The drive you just bought is already formatted

Almost every external drive ships exFAT, because that mounts on the widest range of machines in the shop.

That is a decision made in a warehouse, not advice aimed at you. If the drive is going to live on your Mac, reformat it before you put anything on it. Doing it on day one costs nothing. Doing it in a year means moving the contents somewhere else first.

Disk formatting always erases. Disk Utility does offer to convert a Mac OS Extended volume to APFS without erasing, but that is the only in place move available. It does not apply to exFAT or to a Time Machine volume.

The short version

Mac only, on flash, APFS. Mac only, on a platter, unencrypted Mac OS Extended. Time Machine, APFS. Shared with Windows, exFAT and eject it properly every time. Camera or console, whatever the device asks for, formatted by the device.

The one habit worth building is to decide before the drive has anything on it. Every format decision is cheap on an empty disk and expensive on a full one.