Ndaga Fijo › Guides › Windows USB on Mac

Bootable USB for Windows on Mac: how to create one

By Festo Kasalu Magembe · Updated 26 October 2026

To make a bootable USB for Windows on a Mac you need more than a copy in Finder. Windows installers are the awkward case on macOS. A Windows ISO isn't a "hybrid" image you can copy block for block, and its biggest file usually breaks the FAT32 limit. This guide shows the reliable way, using Ndaga Fijo, and explains what's happening so you can fix problems.

What you need

A Mac running macOS 13 or later (Apple Silicon or Intel).
A USB drive of 8 GB or more. Everything on it will be erased.
A Windows 10 or 11 ISO from Microsoft, and Ndaga Fijo.

Step by step

Get the ISO from Microsoft's download page, and check its SHA-256 against the value Microsoft publishes. Ndaga Fijo's Checksums button computes it for you.
Open Ndaga Fijo and drop the ISO onto the window. It reports "ISO image: files will be extracted to the drive", which is correct for Windows.
Pick your USB drive. Only removable drives are listed, and the disk macOS runs from is never offered.
Open Options if you want to change anything. For most PCs from the last decade, MBR + FAT32 boots in both UEFI and legacy BIOS mode.
Click Write to Drive, confirm the drive name, and enter your Mac password (writing to a disk needs administrator rights).
Wait for Your drive is ready, click Eject, and boot the target PC from the USB drive.

What happens under the hood

The app formats the drive, copies the ISO's files, and handles the two Windows-specific problems:

The 4 GB limit. If sources/install.wim is larger than FAT32 allows, it's split into install.swm, install2.swm and so on. Windows Setup reads split images natively. Details here.
Booting on older PCs. For MBR + FAT32 media containing bootmgr, it installs the Windows MBR and FAT32 boot record so legacy BIOS can boot. UEFI machines boot from the files alone.

Speed. To avoid thousands of slow per-file writes to the stick, it builds the drive on your Mac's SSD first and then streams it across in one pass. In our test that was 14× faster than copying the files directly. See the benchmark.

If it doesn't boot

Choose the USB entry in the boot menu (often F12, F10, Esc or Option on a Mac).
If the PC is UEFI-only with Secure Boot, keep MBR + FAT32 or switch to GPT; both carry the UEFI boot files.
Try another USB port, and avoid USB hubs.
Still stuck? Copy the app's log (Log → Copy) into a GitHub issue. We haven't verified booting on every machine and want to hear what you find.

FAQ

Can I just copy the ISO's files in Finder? You can, but the drive won't have boot code for older PCs, a large install.wim won't fit on FAT32, and the copy is slow.

Why not write the ISO directly? Direct writers need a hybrid image. Windows ISOs aren't hybrid, so a block-for-block copy usually won't boot.

Download Ndaga Fijo