2 ways to change file name extension on Mac

Like Windows, Mac system hides all file extension by default. To rename a file on Mac, you shoud first make sure the file extensions are shown.

Show all file extensions on Mac

Here is the method to display extensions for all files, even those that have "Hide externsion" option checked in Get Info windows. To do so, open Finder, and go through Preference > Advanced to check the 'Show all file extensions' box.

Option 1: Change Mac file extension directly

Click twice on the filename (two slower clicks), or hit Enter when highlight a file, the file name and extension will turn changable. After the file extension is given, hit Enter to confirm.

Option 2: Change file extension in Get Info window

Highlight the file and hit Cmd-I (Command key next to the space bar). Change the file extension and click on the Red button to close.

Done. Now you can open the file with the new default program for thie type of files.