When trying to format a flash drive in Windows (7 or 10) you will see the file system options best suited for the device. The proper file systems for a flash drive is: FAT, FAT32 or exFAT. Windows provides NTFS as an option for USB flash drives, but as mentioned before, NTFS is not the best file system for a USB drive. During the format process, only the best suited file systems will be displayed in Windows.

Why is UDF not listed as an option?

First, let me say it IS possible for Windows to format a USB flash drive as UDF (Universal Disk Format). Microsoft just doesn’t want you to do it; and with good reason.

Before you get too far: If you think formatting a flash drive as UDF will make the thumb drive appear as an optical drive in the computer – you are mistaken!

From the Wikipedia page about Universal Disk Format, UDF, the specification is governed by the Optical Storage Technology Association and because of that, many believe a UDF anything will work like a disc. It, UDF, is most widely used for DVDs and newer optical disc formats, can be used on flash drives, but does make it operate like one.

If we take out the hope of formatting a USB with a UDF file system, some may feel the Universal Disk Format means the flash drive will work in anything, such as from Windows, to Mac, to Linux, Symbian and/or to proprietary system. The truth here is exFAT will do just the same. Please keep that in mind.

So why not format a USB as UDF in Windows? Here is a list:

• The lack of fully-functional filesystem check tools.
• 64GB limit with Windows & Linux, a bug, not a limit of UDF
• SD and USB mass storage devices are exposed to quick wear-leveling failure
• UDF is read-only for Windows XP

Without bogging down this post with ultra-technical information, from the above list, the most important to consider is the first, lack of filesystem check tools.

This means if the USB is pulled out while in operation and a bit is affected by the action, there are no tools to check the file system for errors. You are flying the dark as to why the USB no longer works and there are no tools available to help you figure it out. Given the flash drive was specifically designed to be portable and quick access, the above action is most certainly going to happen sooner or later, which makes UDF a high risk file system.

How to format a flash drive as UDF:

Connect the USB to your computer and note the assigned drive letter