File extensions describe to the operating system the type of file in question and indicate which program is needed to access its contents. The simplest way to change the extension of a file is to save it using a different format. Just changing the file extension in the item name does not change its nature and causes problems to arise when the operating system attempts to access the file. On Windows and Mac OS X systems, file extensions are often hidden. This article describes the steps required to change the format of a file using virtually any software program, and also shows you how to make file extensions visible on both Windows and Mac OS X systems.
Steps
Method 1 of 4: Change the Extension of a File Using Any Software
Step 1. Open the file using the default program
Step 2. Access the "File" menu and choose the "Save As" option
Step 3. Select the folder where to save the new file
Step 4. Name the file
Step 5. From the "Save As" dialog, locate the drop-down menu for the file type
Normally the following menu is called "Save as type:" or "Format".
Step 6. From the drop-down menu in question, choose the format of the new file
Step 7. Press the "Save" button when finished
The original file will not be modified and will remain open within the program window.
Step 8. Locate the new file in the folder you chose for saving
Method 2 of 4: Make File Extensions Visible in Windows
Step 1. Log in to the "Control Panel"
To do this, open the "Start" menu and choose the "Control Panel" option. If you are using a Windows 8 system, select this link.
Step 2. From the "Control Panel" window, choose the "Appearance and Personalization" category
In Windows 8, select the "Options" icon present in the "View" menu tab
Step 3. Click the "Folder Options" icon
Step 4. From the "Folder Options" dialog that appeared, choose the "View" tab
Step 5. Make file extensions visible
Scroll through the list in the "Advanced Settings:" box for "Hide extensions for known file types". Uncheck the relevant check button.
Step 6. When finished, press the Apply and OK buttons in succession
Step 7. Open an "Explorer" window to be able to view the file extensions
Method 3 of 4: Make File Extensions Visible in Windows 8
Step 1. Open a "File Explorer" window
Step 2. Go to the "View" menu tab
Step 3. Select the "File Name Extensions" checkbox located in the "Show / Hide" section
Step 4. The file extensions will be visible by opening a new "File Explorer" window
Method 4 of 4: Make File Extensions Visible on Mac OS X
Step 1. Select an existing "Finder" window or open a new one
To switch to the "Finder" window, you can also select the desktop.
Step 2. Access the "Finder" menu and select the "Preferences" item
Step 3. From the "Finder Preferences" window that appeared, click on the "Advanced" item
Step 4. Select the "Show all document name extensions" checkbox
Step 5. Close the "Finder Preferences" window
Step 6. Open a new "Finder" window
All file extensions will now be visible.