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How to Remove File Type Associations Using Registry Editor

Associating a file type with a program can be done using several ways, such as using the Open with… dialog and selecting the “Always use this app to open” checkbox, or via Default Programs or Default Apps. While you can set or change associations using GUI, there is no option provided to delete an existing file type association.

This post tells you how to remove file type associations using the Registry Editor.

Remove a File Type Association Using Registry Editor

Let’s say you’ve incorrectly associated a file type named .bak, and want to remove the association. Use these steps to remove the file association settings (for .bak) from the registry.

Before proceeding, create a System Restore Point. Additionally, export each registry key listed below to a .reg file prior to deleting, just in case you need them.
  1. Start the Registry Editor (regedit.exe), and go to this branch:
  2. Note down the (default) value data in the right pane. It’s the ProgID associated with that file type.
  3. Right-click the key .bak, and choose Delete. Click Yes to confirm.
  4. Go to the following HKEY_CURRENT_USER keys and delete the .bak key.

    This should remove the file association settings for .bak file type. The deleted file type should now be treated as unknown by Windows; which is exactly what we wanted.

    Delete the Progid as well (optional)

    If you also want to clean up the ProgID key for that file type, which you noted (bak_auto_file) in Step #3 above, you must do so only if that ProgID bak_auto_file is not used by any other file type. This is important.

    How to find if any other file type(s) is mapped to the same ProgID?  Do a search (for Data containing the ProgID string – match whole string only) in the Registry Editor. Or run one of the commands given below to find it out.

    This time, let’s take the example of txtfile Progid. To view the list of file types that use the txtfile ProgID, run:

    Example: txtfile (progid used for .txt)

    assoc | findstr /i "txtfile"


    reg query hkcr /d /f "txtfile" /s

    In the above case, the following file extensions are still using the txtfile progid:

    .LOG | .SCP | .TXT | .WTX

    So, you should not remove the HKEY_CLASSES_ROOT\txtfile registry key, as it would break the association settings for other file types that use this key.

    Now, let’s use the above method and find out if any other file extensions are using the bak_auto_file Progid. Running the command for bak_autofile, you get this:

    As no other file types are using this ProgID, you can safely delete this key:



To remove the file association settings for .bak file type, we’ve deleted the following registry keys:


That’s it! Hope this guide helped you delete an unwanted or incorrect file type association on your Windows computer.

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