Blocked folder names in Windows 10

If you try to create a folder in Windows 10 called “con” you will get a surprise – it’s not allowed.

Instead you get an error which reads

The specified device name is invalid.

What device and why?

This happens because “con” is a reserved system term in the Windows operating system and it’s been like that all the way back to Windows DOS.

These terms are used to access devices – therefore they cannot be used for folders or files.

And there are others, including:

  • CON
  • PRN
  • AUX
  • NUL
  • COM1
  • COM2
  • COM3
  • COM4
  • COM5
  • COM6
  • COM7
  • COM8
  • COM9
  • LPT1
  • LPT2
  • LPT3
  • LPT4
  • LPT5
  • LPT6
  • LPT7
  • LPT8
  • LPT9

But name name is Con and I want a folder!

If you really wanted to create a folder using one of these names your best bet is to replace a character with a similar character.

For example, instead of the O you could use a 0 (zero) – e.g. c0n

There are other options, such as adding an invisible space using the ASCII character 255 – but it’s not recommended.

Help!  I’ve managed to create a folder a cannot delete!

There are ways to create these folders – but you end up with a folder you cannot open or delete.

You’ll just get an error which reads

The handle is invalid

See Windows 10 – How to delete “The handle is invalid” folders for how to delete these folders.

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