FORBIDDEN Windows Filenames 

Note: Those device names go back a lot further than dos. I recall them being reserved in the Whatfor FORTRAN compiler back in about 1970 -- my first programming language, FORTRAN 66.

Your voice, pronunciation and clarity of language is really appreciated.

I'm old enough to remember when just making the file "c:\program" would end any windows computer

*"You know it's real FORBIDDEN When Thio uses a different font"*

Windows: "I must protect you from yourself" Linux: "Do it, I fucking dare you"

Fun fact: If there's two files or folders with the same name with one followed by < and the other followed by >, Windows will mark whatever directory it's in as corrupted. If you were to do this in Drive C, Windows would throw the bug check NTFS_FILE_SYSTEM on boot for a few times, and then Startup Repair would remove the invalid files.

According to the secretary the computer says "No" but to this video I say yes! More of this!

I remember when I did a script for school related to a cone, and wanted to name it 'con' (Cone is romanian) but windows wouldn't let me so I had to choose a different name It's good to learn why you're not allowed to name your files like this

Ah, that feel when you're old enough to actually have used device names in MSDOS.

If you get stuck with a path length limit you can open a command prompt and use the SUBST command to map a drive letter to somewhere deep enough in the path tree. Then you can use Explorer to move (or shorten the names of) files and folders until the items are within the limit for the actual drive/volume. This will help get you out of a jam, but I *strongly* recommend against using SUBST as a permanent solution. IIRC you can also share one of the folders in the tree and it will pretty much work the same.

Path Length Limits, this has been pissing me off for a while and never understood what was going on. Thanks dude, appreciated :)

12:00 : People who followed him without listening to what he had to say must have been like *Bruh*

Fun fact, if you create one of these files in a synced to OneDrive folder it will allow you - but give a notification telling you the file/folder can't be synced. Try it out!

I'm enjoying these more technical videos! Keep doing more of these!

1:09 Now we finally know ThioJoe's actual name

This is great! As COM1 is just a file, you can read and write to a serial port from CMD! Very handy for Arduino stuff!

1:00 - The reason that some Unicode characters don't work either is because Windows treats filenames with "special" (read non-ASCII) characters as long-filenames even if they're not literally "long", and when it tries to create a short-filename (8.3) entry for it, it tries to use the closest substitutes for them that it can, so when you try to create a file called LPT¹, it tries to create a SFN called LPT1 which isn't allowed, so it fails. The LFN-SFN substitution mapping has limits, so some do work. 3:00 - It's not just empty files that are stored directly in the MFT instead of in clusters, even small (

I doubt that anything here will ever be really pertinent for my work at my computer, but it’s interesting enough, and when you have gone to the trouble of making a video like this, the least I can do is honor what you have done by watching to the end.

To get around the deep path filename restriction while copying a deep folder to another, just leave a pointer from folder 1 to folder 2, a.k.a a shortcut..

TomScott made this video too, but you explain it in deeper details :)

4:00 more on this, I guess: in (as far as I know) all modern filesystems, folders and files are basically the same thing - folders are just files that contain references to other files. this lets the computer treat them more or less the same, and also that all of the usual naming restrictions on files also applies to folders.

I love to drop in and refresh things I know and learn new stuff. Thanks

I remember DOS, where you had 8 characters max for the file name and 3 for extension. That's it.

Thank you for introducing me to F.Lux!

49 seconds ago...😂 What am I doing with my life

Tom Scott: Why you can't name a file "Con" in Windows

On really old computers, you can redirect any stdout text that would normally go into the console to the null character device, as writing to stdout can take up a lot of CPU cycles.

I started using computers in 1982 with the Tandy TRS-80 this brings back memories. Thanks

You can also use wsl to create one by running touch con. rm con also works just fine.

Really Great. Video Thio

I remember when the RSTS/E operating system on PDP-11s had similar mechanism for naming devices as files.

Everytime ThioJoe has a new upload I auto drop everything I'm doing.

Thanks for making this video. I always wondered why.

Love Your Videos! Love From Dubai! ❤️🇦🇪❤️

On Windows 11, I was able to use the command prompt to rename an existing text file to LPT1.txt. Windows 11 also had no issues opening, deleting, copying, etc. the file. Out of curiosity I decided to copy it onto a USB, and plug it into a Windows XP laptop. There, it had the issues with copying it and deleting, etc. Windows XP's command prompt also did not allow renaming a file to LPT1.txt. TL;DR, on Windows 11, using these file names works better than on older versions of Windows.

Fun fact: Some versions of the default Android Camera App used "aux.jpg" as the name for low-resolution previews of some images, so if you had set up automatic backups in Google Drive/Google Photos on a device with that version installed, it would create lots of undeletable files on any Windows PC that was set up to sync your Google Drive folder.

3:57 i use this to keep programs from doing certain things. Ie stop a program from filling up a cache for ads (i assume to show when offline); I delete the ad folder and replace it with ad file and it can no longer save to that folder.

long file name (255 chars) error is something that I run into frequently at work. Civil engineering projects get to be very complex and the project names are large to begin with.

Great series of videos

in macOS the only forbidden characters in file names are ":" and "/". ":" was used as a path seperator in really ancient versions of mac os before they switched to /. i guess they still have the ":" forbidden for backwards compatibility even though they literally removed all x86 app support from macOS for no reason. edit: macOS also has device files but they are all in /dev so you can create files/folders with those names in other folders

You can also create one of these 'Unkillable' files in the Android OS. I found this out the hard way. I'm not sure if Linux would be able to delete them but BSD UNIX could using Hex notation for the file name. I'm not sure if you can use hex notation for file naming in either the CMD she'll or the PowerShell.

ThioJoe: Forbidden Windows Filenames Everyone: *tries to make the forbidden files*

You make me a smarter person, thanks.

Hey Thio, where did you get that hott wallpaper in your background desktops?

nice work, good vid

15:05 .Now I know why this Error used to come... THANKS

very informative

Keep Going bro

Thanks for your sharing

I was able to make some files names that shouldn't be able to be named the way they were, Like I made a folder on my phone called "..." and used adb pull The file couldn't be deleted because windows didnt know its extension, I used 7-Zip to create an archive of it and checked "Delete file after compression"

"Consider liking the video because not everyone does" really hit me hard

Fun fact: save a file in Word for example with the following name: @1,2.docx Then try to rename it from File Explorer File name is like locked 😄

Damm just found this channel... Pretty cool stuff

Hi ThioJoe!

Imma try them now; after all, it's always the "forbidden stuff" that is so good! 👌🏽😈😉

Meanwhile for Linux the only restrictions are that you can't name a file with no name or just the Null character ... ....everything else is possible (some are annoying, and so should be avoided)

ahh yes. I remember the times when I manually fought against worms and malware that uses these forbidden names as their filenames for their payload and stuff. Battle was really tough.

Joe. I have a question. If i buy a new computer will most of all the setting reset? if so i would like to know which settings!

I am super meticulous with my file orginization and I use a ton of folder levels. I run into that file path length limit probably at least 2 or 3 times a month.

The good old serial port is still widely used in industrial environments. It is still the main form of communication between maritime safety and navigation equipment. The NMEA protocol is very simple and easy to work with.

0:09 Funnily enough, you can create them with software written to create files with those names. The blacklist seems to be at shell level (Explorer, standard save dialogs, etc.), not on the WinAPI level. I know, because I once wrote such program in Delphi 7 that created (unremovable by any normal means) files named con in any directory I chose just to mess with the IT teacher in my high school who didn't know a thing about computers and should work elsewhere. That was on WinXP though, but I feel like it would still work. You could also create files with completely empty names (no funny unicode hijinks like a 0 width space needed) using the same method or with forbidden characters.

I used to write Bash scripts for fun, and I used NUL a lot. This video is pretty informative about the other device files. I tried PRN just now and found out it didn’t work for me.

I love his videos they are so amazing

Think of the meme potential with this: Cave of Wonders: INFIDELS! YOU HAVE CREATED A FORBIDDEN FILENAME! Belle: What's in the developer's directory? Beast: _Its forbidden!_

You should have tried using WinRARs "delete files after archiving" feature :)

The maximum file name size means NOT the actual absolute path. You can navigate with Windows Explorer to a directory that exceeds the 254 characters and create a new folder, and a new folder within, then a file. It is even possible to copy those long paths via Explorer using two windows and copy file by file if neccessary. To copy those folders Windows has the on-board tool ROBOCOPY. It is only text-mode based but has several other features like copying from unreliable devices or network connections.

Flashbacks to me a few years ago making random (long and forbidden) variable names when I was learning how to code

At one time the nul device existed on ALL directories. Back in the day, we would redirect all output being set to & from the device CON if all we needed was the data that was written to a separate file that we could use.

At 8:35 the connector he shows is a VGA display connector, technically not a 9 pin serial connector.

Ah, file path length limitations. I have encountered those as well with people who had incredibly long file names inside nested folders each with incredibly long file names as well. Good to know that there is a registry setting for that.

In a VM, I tried to install win10 and created something using the forbidden characters by booting into a Linux Live CD. All were behaving really differently. If I tried to create a folder named C:, Windows would take me to C:\ (i.e. the actual C: drive), and if I try to delete that from within Windows, it would actually try to delete the actual C: drive! Second, if I try to create folders with / and \, some made Windows refuse it's existence and some make explorer to take me into that path, e.g. if I create a folder named Windows\ in the C: drive, it would take me to the actual Windows folder. And again, deleting them would try to delete C:\Windows. Third, I tried to make folders with double quotes and Windows refused it's existence and some gave weird errors like ERROR: CRITICAL ERROR (the descriptive error name ever). Creating folders with < or > in the name did kinda the same thing as the others, but creating two folders, one with < and another with > in Desktop (say), I couldn't get access to the Desktop; when I log in to Windows, it gave me an error saying it couldn't access it. HERE'S THE SCARIEST PART: I CREATED THE TWO FOLDERS WITH < AND > IN THE ROOT OF C:\ DRIVE AND..... GUESS WHAT, IT RENDERED THE OS UNBOOTABLE! Automatic "Repair" didn't work either as it couldn't actually access the C: drive to perform repairs. The only solution was to delete the folders from within Linux Live CD.

Reminds me of the good old IRC chat days, when everyone still had win95. We have sent files with these names to everyone in the chat room. And all had bluescreens.

Dude, >PRN sounds like it's a spooler for the parallel port. I'd like to know if there's any way you're aware of to move a spool file for a printer file into another printer file, ie from _LexMark614_ to _LexMark614-2._ Is it possible to move spool files between printers or is there a way to make output queues for them instead. I hate not being able to just grab an output and gift it to another printer. I'm not worried about formatting - I grew up in a time when the device driver was the connecting rod between the keyboard and the chair.

Very informative vidoe

Hi am your biggest fan thanks for making a video

Can you do a video about the Desktop Window Manager and Antimalware consuming so much ram/gpu

3:17 You Could use 7-Zip as well. The directory for files: :\[SYSTEM]\...

I once downloaded the movie Con Man from a torrenting site. The folder name was Con.Man.2018.1080p and after downloading it I couldn't move it nor delete it nor rename it. I learned to live with it in my computer. Until a few months ago when it dawned on me. I mean, I knew about this, I just forgot about the CON reserved word in my folder name..

I understand the behind mechanism of Drivers and how they work. The Basic stuff.

I had a forbidden file. I had a hard drive with a Linux distro and it had the application for running Windows applications called wine. It actually created a file within its structure for corresponding drive letters (e.g. it had a file called c:) which I eventually copied my entire home drive to an external hard drive before nuking my Linux install. This file was backed up to my external drive and Windows will NOT let me remove it.

🤔Could be an interesting way of making sure a folder with important files doesn't get deleted.

TJ, 8:40ish ~ IMG of "Serial port" was 15 pin "VGA Port".

He! you should make a video on what happens erase the reserved NTFS file names! I really would like to see what happens

virtually every program is written assuming the old fixed path length limit. Changing the registry to enable unrestricted path lengths doesn't mean any other program will work with them so be very careful if you enable the option; programs may fail to open files, crash or worse

you can still access a folder if the file with no extension has the same name as the folder just when you are typing the path add a extra \ and it will move you to the folder

An example of device files outside of windows is: /dev/devicename... It's like that in all Unix and Linux systems... An example is /dev/sda1 (device, sata device a, partition 1)

yea I ran into this problem when I was cloning a git repo, one of the files in it used 'aux*.png' in the name. Deleting my local copy of the repo became a real pain. Having to go into safe mode and removing it that way or using something like 7-zip to rename or mingw bash emulating terminal to delete it. Super annoying.

Some app: *hiding the name* System: “is this crusty crabs?” File: “No, this is Patrick”

Hi ThioJoe do you remember DOS 3.1?

Is there a utility or script to auto change file names in windows to replace a colon(:) with a dash?

You should do a video on naming a user with those device names in windows 7 cuz it was patched up on later versions of Windows

Nice video

Fun Fact about forbidden characters: Having a file/folder with < and another with > in the same directory will make Windows treat the folder those two are in as corrupted (Don't do it in the C: directory)

Is this for folders as well? Then I might have to name my important folders PR0N instead of PRN...

How do you make the super/sub script numbers?

The ability to create forbidden files using UNC is potentially a major security hole. Imagine for a second what would happen if a bad actor attempts to create a malicious executable named “COM1.exe” for instance - would be impossible for antivirus software to remove.

NUL is still very useful and used quite often especially in batch files

Let's admit it, we all were thinking of PRN as something other than the printer

Tom Scott did a video about this.

As an IT professional: The file length limit is not a edge limit. Some customers just seem to thrive on overly long and complex folder structures. Luckily, the long file name support can also be enabled per GPO.