Set Your Computer to See File Extensions
For both Windows and Mac

Table of Contents

What are file extensions?

File Extensions Galore!

There are hundreds of file extensions. The following sites can help you identify the meaning of file extensions that you may not be familiar with:

  4. File extensions reference

Setting your Mac to display file extensions

You will now set your Mac to make file extensions visible. Please do the following:

  1. First, open to the Finder's Preferences.
    1. If you don't know how to select the Finder, hold down the Apple (Command) key (  ⌘ ) on your keyboard and, as you hold it down, tap on the Tab key until you select the blue smiley Finder icon: Mac Finder Icon then let go of the keys.
    2. Now you are to set you to the Finder.


  1. From the Finder menu (it is to the right of the Apple menu  - see illustration below), select Preferences... (item 1 in the illustration below).
  2. In the Finder Preferences dialog box ( 2 ).
  3. Enable Show all file extensions ( 3 ).

    Setting Macs to show file extensions

Setting Windows to display file extensions

Try these methods abbreviated instructions first:

You may prefer my instructions for Windows 7:

  1. Right click on Window's Start button.
  2. Select Explore or Open Windows Explorer or something similar (it depends on your Windows version).
  3. Windows Explorer (or File Explorer) will open.
  4. On the left side of the menu bar click on the Organize button and select Folder and search options from the menu.

  5. In the dialog box that opens, click the View tab.
  6. In the Files and Folders section DE-select (disable) Hide extensions for known file types. *
  7. Close the dialog.

* The words "known file types" suggests that there are file extensions that are unknown to anyone, which is probably not true.

Setting Windows to display "details" view

You will now set Windows to provide optimal information about the files.

My instructions for Windows 7

  1. Open Windows Explorer if it is not already open:
    1. Right click on Window's Start button in the lower left corner.
    2. Select Explore or Open Windows Explorer or something similar (it depends on your Windows version).
  2. Windows Explorer will open.
  3. On the upper right side of the menu bar there is a button that lets you set the type of view of folders and files to either icons, names, or various combinations of the two (see next illustration). If you hover over the button, a tool tip appears: Change your view
  4. Select Details. I always recommend using Details view because it provides the most information.

Note that if you want to display Details view in the subsequent Explorer windows that you open:

  1. Follow steps 4-5 in the Setting Windows to display file extensions section above.
  2. In the top part of the dialog, in the Folder views section, select Apply to Folders, then OK it.

Comparison of Large Icons and Details views

Icons view

Details view