Erase Windows-formatted USB on Mac

🔧 How to Erase a Windows-Formatted USB Stick on macOS (NTFS/FDisk) and Reformat for macOS Use

Have you ever plugged a USB stick into your Mac only to find that Disk Utility doesn’t see it properly, or it shows up with a strange layout like “FDisk_partition_scheme”? Here at wansec, we sometimes need to erase Windows-formatted USB on Mac. If your USB drive was previously used for a Windows installer or had an NTFS or FAT32 partition, macOS may struggle to format it cleanly using the Disk Utility app.

In this article, we’ll walk you through:

• What causes this issue
• How to check your USB’s current format
• How to fully erase and reformat the USB stick via the command line

🧩 The Problem: Disk Utility Can’t Erase the USB Properly

macOS’s Disk Utility sometimes can’t erase or repartition USB drives that were:

• Used as a Windows installation drive
• Formatted with MBR (FDisk_partition_scheme) instead of GPT
• Have NTFS or hybrid partitions

This can result in:

• Only partial space being shown (e.g., 34GB on a 64GB drive)
• Greyed-out erase options in Disk Utility
• The drive not mounting or not being fully visible

🔎 Step 1: Check the USB Drive in Terminal

Even if Disk Utility doesn’t show the disk, Terminal often will.

diskutil list

Example output:

/dev/disk4 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *61.5 GB    disk4
   1:             Windows_FAT_32 ESD-USB                 34.4 GB    disk4s1
                    (free space)                         27.2 GB    -

Here, we see:

• A 64GB USB stick using FDisk (MBR)
• A single FAT32 partition (Windows-style)
• Unallocated free space

macOS reads the layout but can’t manage it properly.

💥 Step 2: Erase the Entire Disk from Terminal

Use this command to fully wipe and reformat the USB disk:

diskutil eraseDisk HFS+ MyUSB GPT /dev/disk4

Replace /dev/disk4 with your actual disk ID from the previous step.

What this does:

• HFS+ formats as Mac OS Extended (Journaled)
• MyUSB is the volume name (changeable)
• GPT sets the GUID Partition Table

⚠️ Double-check your disk ID to avoid wiping the wrong disk.

🏁 Wrapping Up

USB sticks formatted for Windows can be tricky to reset on macOS, especially with NTFS or MBR layouts. When Disk Utility falls short, Terminal gives you full control to:

• Wipe out old partitions
• Create a fresh, macOS-friendly format
• Fully reclaim disk space

Whether you’re prepping a macOS installer or just trying to clean up an old USB stick, now you know the right way to do it.

Have you had success trying to erase your Windows-formatted USB on Mac? If you plan to create a bootable USB stick, I suggest you check balenaEtcher.

Need help with macOS installers or USB tools? Leave a comment below — happy to help!