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Making a Mac OS Extended (HFS+) USB Drive on Windows with TransMac

By Wes Ellis4 min read

Most of my vintage Mac software lives on a Windows machine, which is a little ironic. The problem is getting it back onto the Macs. Windows can't write HFS+ (Mac OS Extended) at all, and the old Macs don't know what to do with NTFS or exFAT.

The tool I keep coming back to is TransMac from Acute Systems. It's paid software with a 15-day trial, and it's the least fussy way I've found to format a USB stick as HFS+ and copy files onto it from Windows.

What you need

  • A Windows PC and admin rights on it (TransMac needs them to write to disks directly)
  • A USB drive you don't mind erasing
  • TransMac, from acutesystems.com
  • The files you want to move

Format the drive

  1. Plug in the USB drive. If Windows pops up "You need to format the disk," click Cancel. Don't let Windows anywhere near it.
  2. Run TransMac as administrator. Your drives show up in the left pane.
  3. Right-click the USB drive and choose Format Disk for Mac.
  4. Give it a volume name and confirm. This erases everything on the drive, so double-check you picked the stick and not your backup disk. The drive list doesn't give you much to go on besides size.

Copy files onto it

Double-click the drive in TransMac's left pane to open it. From there you can drag files in from Explorer, or use the copy buttons in the toolbar. It's not fast. Big files crawl a bit compared to a normal NTFS copy, so go make coffee.

When it's done, close TransMac and eject the drive from the Windows tray like any other USB device before pulling it.

Before you plug it into an old Mac

This is where the retro part bites.

HFS+ needs Mac OS 8.1 or later. Anything older only reads the original HFS (Mac OS Standard) and will offer to initialize the drive. Say no. For a System 7 machine you're better off with a CD, a floppy, or a network transfer.

Classic Macs and USB are a mixed bag. USB only shows up on the iMac G3 era and later, and some older Mac OS versions are picky about large drives. A small, old stick is often friendlier than a new 128 GB one.

Booting is a different problem. A PowerPC Mac expects an Apple Partition Map to boot from. If you want a bootable installer rather than a file-transfer drive, it's usually easier to build it on a Mac with Disk Utility. TransMac can also write a .dmg image straight to a drive (the Restore with Disk Image option), which is handy for installers that come as images.

Resource forks can get lost. Classic Mac apps keep a lot of themselves in the resource fork. If a program on the stick won't open or shows up as a generic document, it probably lost its fork somewhere between the original download and your PC. Keep software in .sit, .hqx or .dmg form while it's on Windows, and only expand it once it's on the Mac.

When it doesn't work

  • TransMac doesn't show the drive. Run it as administrator, and try a different USB port. Front-panel ports and hubs cause more trouble than you'd think.
  • The format fails. Unplug, replug, and try again. If it keeps failing, wipe the stick with diskpart (select the disk, clean) and then format it in TransMac.
  • The Mac says the disk is unreadable. Check the OS version against the HFS+ rule above.

Other options

HFSExplorer is free and will read HFS+ volumes on Windows, but it can't write to them, so it's only half of the job. Paragon's HFS+ for Windows is a paid driver that makes the drive show up in Explorer like any other disk, if you do this often enough to want that.

TransMac is still the one I reach for. Label the stick "Mac" with a marker, though. Windows won't be able to read it without TransMac installed, and you'll forget which one it was.

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