Volume Serial Number

Volume Serial Numbers, How They're Generated, & How to Change Them

Photo of a computer screen showing random hexadecimal code
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A volume serial number, sometimes seen as VSN, is a unique, hexadecimal number assigned to a drive during the creation of the file system, during the format process.

The volume serial number is stored in the disk parameter block, part of the volume boot record.

Microsoft and IBM added the volume serial number to the format process in 1987 when they were working together to develop the OS/2 operating system.

Note: A drive's volume serial number is not the same as the serial number of the hard drive, floppy disc, flash drive, etc. assigned by the manufacturer.

How is the Volume Serial Number Generated?

A volume serial number is created based on a fairly complex combination of the year, hour, month, second, and hundredth of a second that the drive was formatted.

Because the volume serial number is generated during the format, it will change each time the drive is formatted.

How to View a Drive's Volume Serial Number

One of the easiest ways to view a drive's volume serial number is via Command Prompt, using the vol command. Just execute it without any options and you'll see both the volume serial number, as well as the volume label.

Not comfortable with commands or need some more help? See my How to Find the Volume Serial Number of a Drive From the Command Prompt tutorial for a detailed walkthrough.

Duplicate Volume Serial Numbers

Since volume serial numbers are not generated at random and without knowledge of the volume serial numbers on other drives in the computer, there's a chance that two drives on the same computer could end up having the same volume serial number.

While the probability of two drives in a single computer getting the same volume serial number is technically possible, the chance is infinitesimally small and isn't usually a concern.

The only somewhat common reason why you might run in to two drives in the same computer with identical volume serial numbers is when you've cloned one drive to another and are using them both at the same time.

Are Duplicate Volume Serial Numbers a Problem?

Duplicate volume serial numbers are not an issue for Windows or other operating systems. Windows will not be confused as to which drive is which if two drives have the same volume serial numbers.

In fact, the volume serial number is used by some software licensing schemes to make sure that an installed copy of software is being used on the correct computer. When cloning a drive, and the volume serial number remains, it helps ensure that the software you run on the new drive works as you'd expect.

Another piece of data called the disk signature, part of the master boot record, is the truly unique identifier for a hard drive in a computer system.

Changing a Drive's Volume Serial Number

While there's no built-in ability in Windows to change a drive's volume serial number, there are some free, third-party tools that will do the trick.

Your best choice is probably Volume Serial Number Changer, a free, open source program that shows you some basic information about your hard drive, plus a small field to enter the new volume serial number you want to set.

Another option is Volume Serial Number Editor. This program is very similar to Volume Serial Number Changer but this one isn't free.

Advanced Reading on Volume Serial Numbers

If you're interested in finding out more about how volume serial numbers are generated, or how you might be able to tell something about a formatted drive by deciphering the number, I recommending checking out this Digital Detective's whitepaper:

Volume Serial Numbers and Format Date/Time Verification [PDF]

There's more in that paper about the history of the volume serial number, as well as how to view it directly from the boot sector.

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