Create Mac OS X bootable USB disk

Open a Command Prompt as Administrator (Start → CMD) and prepare the USB stick with diskpart:

diskpart
list disk
select disk X    (X is the number of your USB flash drive)
clean
convert GPT
create partition primary

Double-check the disk number before clean — it wipes the selected disk without confirmation, and picking the wrong number destroys your data.

Then you can use a program to transfer the DMG image to the USB disk. TransMac from Acute Systems is the classic choice: acutesystems.com/scrtm.htm.

Use any method you like to download the macOS version you want — but stick to trusted sources; a tampered image is the main risk here, and the hash-check habit is worth keeping.

Reading this in 2026

• The Apple-supported path is a Mac: the official procedure (Create a bootable installer for macOS) is done from macOS itself — download the installer, then createinstallmedia onto a 16GB+ USB drive. How to download and install macOS covers getting the installer.
• From Windows without a Mac: the diskpart + TransMac flow above still works as the DIY route (TransMac is shareware; verify current builds on the Acute Systems page). A handful of open-source GUI helpers exist, but they come and go — check that any tool you pick is actively maintained before trusting it with your media.
• Newer Macs need newer installers: Apple silicon and T2 Macs only boot macOS versions signed for them — an old Snow Leopard USB won’t help on an M-series machine. Match the installer to the hardware.