How to change default apps (Windows)

Changing default apps

To change the software that starts when you double-click on a file (default apps), follow the next steps.

  1. Right-click on the file and select “Open with (プログラムから開く)” → “Choose another app (別のプログラムを選択)”.

  2. Then a window like the following will appear. Choose the software (app) you want to launch.

  3. After selecting the software (app), click on the “Always(常に使う)” button.
  4. Thereafter, if you double-click on a file of the same type (extension) from the next time, the software (app) selected above will launch.

On file name extensions

Character strings after “.” (Dot) on the end of file names are called extensions. They are attached so that OSes (and humans) can easily identify file types. (But it is not compulsory: one can add a file name which does not have an extension, or add an extension not related to the file type.)


.pdf       PDF (Portable Document Format) file

.docx     Microsoft Word file

.txt       text file

Windows has a function to associate software (application) for each extension, which is the “default apps” above.

Please also note that file name extensions are hidden under the default setting of Windows. To check the setting whether show or hide file name extensions on Windows 11, launch the Explorer, click on the “View (表示)” menu on the upper menu and check the “Show (表示)” → “File name extensions (ファイル名拡張子)” is checked.

Folder Option

If you want to display file name extensions, check there.

Example of file name display:

  • Hiding extensions
  • Showing extensions