Try it yourself right now. Open Windows Explorer, attempt to create a new folder named "con", and watch as your computer flatly refuses. Not "con folder", not "my con files"—just the three letters C-O-N by themselves. Windows won't allow it, and this isn't a bug. It's a deliberate design choice that traces back to the 1980s.

This bizarre restriction exists because CON is a reserved system name in Windows, inherited from MS-DOS. It stands for "console"—the keyboard and screen that let you interact with your computer. Back when MS-DOS ruled personal computing, certain device names were hardcoded into the operating system itself.

The Full List of Forbidden Names

CON isn't alone in this quirky club. Windows reserves several three-letter device names that you absolutely cannot use for files or folders:

CON - Console (keyboard and screen)
PRN - Printer
AUX - Auxiliary device
NUL - Null device (discards all data)
COM1-COM9 - Serial communication ports
LPT1-LPT9 - Parallel printer ports

These names are reserved regardless of file extension. You can't create "con.txt" or "prn.docx" either. The restriction applies to the name itself, full stop.

Why This Still Matters in 2025

Nobody uses serial ports or parallel printer connections anymore, so why does Windows still enforce these ancient rules? Backward compatibility. Microsoft has maintained this restriction for decades to ensure old software continues working. Programs written in the 1990s might still reference these device names, and breaking that convention could cause unexpected failures.

The implementation runs deep. These aren't just names Windows checks against a list—they're treated as actual devices at the filesystem level. When a program tries to access "CON", Windows interprets it as a request to interact with the console input/output, not a file or folder.

The Workaround (Sort Of)

Technically savvy users have discovered ways to create folders with these names using special Unicode characters or network path syntax, but these are exploits rather than features. The files created this way often can't be deleted through normal means and can cause system instability. It's not recommended.

Linux and macOS have no such restrictions—you can create a folder named "con" without any issues on those systems. This is purely a Windows quirk, a living fossil from the MS-DOS era that persists in every version of Windows released to this day.

Next time you're organizing files on your Windows PC, remember: you can name folders almost anything you want. Just don't try to go retro with "con", "prn", or any of their reserved device cousins. Windows will politely but firmly decline, protecting decades-old conventions that modern computers no longer actually need.

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