An external hard drive is the fastest way to move a folder off a Mac: no upload, no monthly bill, no internet connection needed. It's also easy to do wrong, in ways that only show up when you need the copy back. Here's how to copy files to an external hard drive on a Mac without losing anything or discovering the copy is unreadable later.
Pick the right format first
Before you copy anything, check how the drive is formatted. It matters more than it looks:
- exFAT reads and writes on Mac, Windows and Android, with no practical file-size limit. It's the safe default if the drive will ever touch another kind of computer.
- APFS is Apple's own format. It's a little faster on a Mac, but Windows can't read or write to it without extra software.
- A drive fresh out of the box is often already formatted a way macOS can use as-is. Check in Disk Utility before you assume you need to reformat.
Reformatting erases everything on the drive, so decide the format and do it first, before a single file is copied over. If the drive will only ever plug into this Mac, APFS is fine. If it might end up on a PC or another device, exFAT saves you a second reformat later.
Connect the drive
Plug the drive in and confirm it mounts: it should show up in Finder's sidebar and on the desktop if you have that setting on. If it doesn't appear, check the cable and the port before assuming the drive itself is the problem: a loose USB-C adapter is a more common cause than a dead drive.
Copy with Sync
Sync by Miciniti treats an external drive as a destination the same way it treats a cloud account, so the setup is the same shape either way:
- Add the external drive as a connected drive in Sync, once it's mounted and visible in Finder.
- Create a Backup task and choose the Mac folder you want copied as the source.
- Point it at a folder on the drive so you know where to find the files later.
- Run it. Files copy across; nothing on the Mac is touched.
Sync only copies when you run a task, with no background or scheduled copying, so a task you haven't run yet hasn't moved anything. If you're choosing between Backup, Backup Sync, Restore, Restore Sync and Full Sync, the five sync modes explained covers what each one does and which ones can delete.
Check the copy before you trust it
Don't eject the drive the moment the task finishes. Open it and look:
- Compare file counts and folder size against the original on the Mac.
- Open a handful of the largest or most important files to confirm they're intact, not just present.
- Eject properly from Finder (or the menu bar icon) before you unplug. Pulling the cable mid-write is the single most common way an external drive copy turns out corrupted.
Once you've checked it, the copy is trustworthy. Skip the check and you won't find out anything was wrong until the day you need the drive.
One drive is one point of failure
A drive on your desk is convenient, but it's still one object: it can be dropped, stolen alongside the laptop, or simply fail without warning the way any hard drive eventually can. The 3-2-1 backup rule is the short version of why a single copy, wherever it lives, isn't enough on its own.
Sync doesn't force a choice between cloud and external. The same Backup task shape works for both, so you can run one to a cloud account and a second to the drive on your desk, and the folder survives either one failing alone. Cloud vs external drive vs NAS walks through where each kind of copy earns its place, and if you'd rather start from the cloud side, how to back up Mac folders to Google Drive or Dropbox is the companion guide. If the goal is freeing up space on the Mac itself rather than just adding a second copy, how to free up Mac storage without deleting your files covers that order of operations.
What it costs
Connecting a cloud drive in Sync is free, with one drive and one task. External and USB drives are part of Sync's paid upgrade, along with connecting more than one drive at once, larger transfers per task and removing ads. The upgrade is a subscription or a one-time lifetime purchase, whichever you'd rather pay.
Get Sync
Sync connects Google Drive, Dropbox, OneDrive, Box, Amazon S3, and USB and external drives from one app on Mac, iPhone and iPad, Android and Windows. For the wider picture of connecting cloud accounts alongside a drive, see how to sync files to Google Drive, Dropbox and more.
