File extensions tell your computer what kind of file it is and what types of software programs on your computer should open the file. The easiest way to change a file's extension is to save the file as a different file type from within a software program. Changing the file extension in the file name won't change the file type, but will cause the computer to misidentify the file. In Windows and Mac OS X, file extensions are often hidden. This article describes how to save a file as another file type in almost any software program, as well as how to make the file extension visible in Windows and Mac OS X.
Method 1 of 4:Changing a File Extension in Nearly Any Software Program
1Open a file in its default software program.
2Click the File menu and then click Save As.
3Choose a location for the file to be saved.
4Name the file.
5In the Save As dialog box, look for a dropdown menu labeled Save As Type or Format.
6Choose a new file type for the file from the dropdown menu.
7Click the"Save As"button. The original file will still be open in the software program.
8Find the new file where you chose to save it.
Method 2 of 4:Making File Extensions Visible on Windows
1Open the Control Panel. Click the Start menu, and then click Control Panel. If you're using Windows 8, click here.
2Click Appearance and Personalization. You can find this in the Control Panel.
On Windows 8, in the ribbon, click Options.
3Click Folder Options.
4Click the"View"tab, in the Folder Options dialog box.
5Make file extensions visible. In the Advanced settings list, scroll down until you see Hide extensions for known file types. Click the box to uncheck it.
6Click on Apply, and then click OK.
7Open the Windows Explorer file browser to see the file extensions.
Method 3 of 4:Making File Extensions Visible on Mac OS X
1Select a Finder window or open a new Finder window. You can also click the Desktop to switch to the Finder.
2Click the Finder menu. Next, click Preferences.
3Click"Advanced"in the Finder Preferences window.
4Click the Show all filename extensions box to add a check.
5Close the Finder Preferences window.
6Open a new Finder window. The files will now show their file extensions.
Method 4 of 4:Making File Extensions Visible on Windows 8
1Open Windows Explorer.
2Click the View tab.
3Check the File name extensions box in the View/Hide section.
4Observe the location of file extensions. When you open a new Windows Explorer window, file extensions are visible.