We recommend resetting your USB Drive via the Disk Utility if possible. Choose the preferred file system from the drop-down menu for Format.Select GUID Partition Map as the scheme.Now, Press the Erase button at the top.Select the USB storage device from the left pane.Press Command + Shift + U to open the Utilities folder.Note: Make sure to connect the USB disk to the computer before you begin. Here is how you can reset a USB disk on Mac using both approaches. Sometimes, due to permission or file system issues, we cannot perform the task using the GUI approach. USB drives on mac can be reset using a GUI approach and also via the terminal. You can replace k with something else if you want to change the drive letter. Once you receive the completion message, type assign letter = k and press Enter.Change fat32 to your preferred file system if necessary. Now, type the following commands and press Enter after each one.Make sure you get this right as you could easily format the wrong drive.

Replace # with your USB’s disk number in the next step. Check the Size section, then note your USB’s Disk #.Type and Enter cmd to launch Command Prompt.This scans for bad sectors but takes a lot longer to complete. Optional: Uncheck Perform a Quick Format to do a Full format instead.Right-click your USB drive and press Format.

Type diskmgmt.msc to open Disk Management.Optional: Uncheck Quick Format to do a Full format instead.

From the left pane, right-click your USB drive and press Format.

Press Windows + E to launch Windows Explorer.

How to format usb drive from imac