An association or file association describes installed software associated with a particular file extension or file format. For example, a file with a .TXT extension is associated with Notepad or WordPad in the Microsoft Windows operating system by default. When opening a file (double-clicking the file), the default associated program opens the file. If no program is associated with the file, you’re asked to choose what program should be used.

Operating system terms

  • How to associate a file with a program in Windows.
  • Our file extensions overview provides further information about file associations and extensions.
  • All questions relating to computer files and file extensions.