Whenever you are using your computer different types of files are being opened, whether they are image files, music, text files, documents or executable files. Every different type of file in Windows needs to be told what it is so the appropriate action can be taken and the file can be opened or launched. The file extension, which is whatever text comes after the last period (.) in a filename tells the system what it is and what should be done with the file.
By default Windows has dozens of types of file extension associated with specific actions so they can be recognized on double click. For instance, .EXE launches the file as an executable whereas .TXT opens the file in Notepad or .REG tells Windows the file is a Registry Editor file. As you add more and more software to your system more file type extensions are added to handle the files required by the software.
It’s quite easy to associate a file not recognized by Windows to a specific file format. All you have to do is right click, select Open with and choose the program you want to open it. However, it’s more difficult to do the opposite and remove a known association from a file so it doesn’t launch or open in any program when double-clicked. Although it’s easily possible to change the association in Windows Control Panel from one file type to another, it’s not possible to remove the association entirely. Here we show you some ways to remove file extension associations in Windows.1. Unassoc
For simplicity, Unassoc is almost foolproof and performs the simple task of listing which file extensions are present on the system and lets them be deleted. The program is portable and under 100KB in size. Sadly it is hardcoded to only work on Windows Vista and 7 systems so won’t work on Windows XP, 8.1 or 10. The source code is not available to correct what would be an easy fix.
Usage is simply a case of selecting the file extension in the list and pressing Delete file type to remove the association. The grayed out button will remove the association if it’s present in the current user profile, but most normal extensions are system wide so will not make the button clickable.
Nirsoft’s FileTypesMan is a small management tool to edit files types and extensions. It’s portable and only about 150KB with options to create new extensions, replace file types, save a report and delete selected extensions, including deleting several at once if you choose.
The removal process is a snap, simply load the program, find and highlight the required extension in the window and press Ctrl+Del or go to Edit > Delete Selected Extensions. Multi selections and removals are possible with the use of Ctrl and Shift. The file extension will be completely from HKEY_CLASSES_ROOT in the registry.
3. Default Programs Editor
Default Programs Editor can be installed to Control Panel and used as a better version of the file type, autoplay and default programs settings in Windows. It can also backup and restore settings, edit the context menus for file types, change file type icons, edit the name of a file type and edit the Open with menu contents.
A file type association can be removed in two ways here, either delete the file extension entirely or leave it there but change its file type association to unknown. The end result is the same and a file with the extension won’t be opened by anything.
a. To delete the file extension from the system launch Default Programs Editor, go to File Type Settings and click Delete an extension at the bottom right. Click on the extension in the list and press Delete Extension.
b. To remove the file type association but keep the extension, in Default Programs Editor go to File Type Settings and click Change an extension’s file type at the bottom. Click on the extension in the list and press Next. In the new file type list select Unknown and press Save File Type.
If you click on the save or delete button drop down there is another option to save the action to a .REG file. This is useful because you can use it to quickly unassociate an extension on your own or any other system. Default Programs Editor is portable and the option to integrate into Control Panel is in Settings. Although the program is from 2010 is still works on Windows 10 but requires the .NET Framework 3.5 optional feature installed.
Types is like a simpler and less advanced version of Default Programs Editor. Although it can change file associations, context menus and icons you don’t really need to use those options for a simple extension delete. Types can both delete the extension or just remove the file type association.
a. Completely removing a file extension is simply a case of launching the Types program, finding the file extension in the window and clicking the Delete button or Del on the keyboard.
b. Like Default Programs Editor you can also just remove the file type association but leave the extension present. To do that instead of pressing Delete, select Properties (or double-click). Uncheck the Class box to remove the file type from the extension.
There are portable, command line and installer versions of Types available, the installer can add an entry into Control Panel for easy access.
5. Remove a File Extension Association From Command Prompt
If you don’t want to use a third party tool or for some reason, they don’t work, another solution is to remove the file association using Windows Command Prompt. Windows 7, 8 and 10 have a built-in command line utility called Assoc which can change file associations from scripts and other programs. Here’s how to delete a file type association.
a. Run an administrator Command Prompt by typing cmd into Start and pressing Ctrl+Shift+Enter.
b. To first check the file extension’s current association, add the extension to the command. Replace .extension with the file extension you want to check. Running Assoc without any arguments will show the current associations for all extensions.
c. When you’re sure you have the right extension, type the following to remove the file association:
The command effectively sets the association to nothing which deletes it. There is no success message, to check it worked type “Assoc .extension” and it should say file association not found instead of what was displayed in step b.
6. Using a Fake File Type Association
This solution might sound a little quirky but it does actually work. What you do is associate the file extension with a program which is subsequently removed from the system. The result is the file extension has no valid association because it can’t find the program that is supposed to open it.
a. Find any executable file on your system and make a copy of it. Optionally rename the file to something unique but do not change its extension from .exe. The file can be any type of executable such as a program installer, portable utility, or even an empty text file renamed to anything.exe.
b. Right click on a file with the extension you want to unassociate and click Open with… If Open with has a sub menu click on Choose default program… Press the Browse button and locate the file created in the previous step. The program will appear in the Open with window. Click OK and close any windows or error messages when the temporary program tries to open the file.
Windows 10 users: In Windows 10 the default program window is different but the procedure is the same. After choosing Open with or Open with > Choose another app, click “More apps ?”, scroll to the bottom of the list and select “Look for another app on this PC”. From there choose the executable.
c. Now delete the temporary executable file and it will break the file association. Double clicking on a file with the extension will pop up the Open with window instead of an associated program.
7. Unassociate A File Type From The Registry
What the options above have in common is they all unassociate the file type using the same underlying method, which is through the Windows registry. Adding, removing or changing what happens when a file with a specific extension is double clicked is handled by registry keys. If for some reason the above solutions don’t work then going to the source of the problem might be your last resort.
a. Open the Registry Editor by typing Regedit into the Run dialog (Win+R) or Start Menu search. Navigate to the following registry key.
Substitute .extension for the file extension name you wish to remove, such as .useless or .file etc.
b. Click on the extension key and double-click the (Default) value name in the right pane. Delete the contents of Value data and press OK. This essentially does the same thing as the Assoc command and doesn’t remove the extension but tells Windows not to associate it with anything.
See if the association has been removed by double-clicking on a file with the extension. If the file is still being opened it may also be in the current user profile::
c. In Regedit browse to:
d. Right click on the extension and delete it, then close the Registry Editor.
The association should now be completely removed from the system.
Tip: If you want to give the unassociated extension a more friendly name than just the extension characters, right click on the extension key in HKEY_CLASSES_ROOT > New > String value and enter the name FriendlyTypeName. Double click it and enter the friendly name for the extension.
In Explorer the file will have the friendly name in the Item type column and not just XYZ File.