The ASSOC command in Windows CMD is used to view or modify file extension associations. This command displays or changes the association between a file extension and the file type (defined by the program used to open the file). The ASSOC command is particularly useful for troubleshooting file association problems or for batch scripting to ensure consistent software behaviors across different systems.


The basic syntax for the ASSOC command is:

ASSOC [.ext[=[fileType]]]
  • .ext: Specifies the file extension to associate with the file type.
  • fileType: Defines the file type to associate with the file extension. If fileType is omitted, the command will delete the association for the file extension.


  • No specific options/flags: The ASSOC command itself does not include additional flags. Its functionality is primarily controlled through the arguments passed to it (the file extension and the file type).


  1. View all associations:


    This command lists all current file type associations.

  2. View the association of a specific file extension:

    ASSOC .txt

    Displays the file type associated with .txt files.

  3. Set an association for a file extension:

    ASSOC .txt=txtfile

    This example associates .txt files with the txtfile file type.

  4. Delete an association:

    ASSOC .txt=

    Removes the association for .txt files.

Common Issues

  • Incorrect file association: Sometimes setting or altering file associations incorrectly can lead to files opening in the wrong programs. Always verify changes by opening a file with the extension you modified.
  • Permission issues: Modifying file associations in system-wide contexts may require administrative privileges.


The ASSOC command can be combined with the FTYPE command to manage how file types are handled:

ASSOC .pl=PerlScript
FTYPE PerlScript=perl.exe %1 %*

This sequence first associates .pl files with PerlScript, then specifies that PerlScript file types should be opened with perl.exe.

  • FTYPE: Sets or gets the file types used in file extension associations.
  • START: Opens a file or program, which can test the functionality of new or modified file associations.

For further readings and more detailed documentation, you might visit the official Microsoft command-line reference.