OS X Mavericks: Show and hide filename extensions

This article has been archived and is no longer updated by Apple.
Show and hide filename extensions

Filename extensions—the period followed by two or three letters you see at the end of some filenames (for example, .jpg)—determine which app can open a file.

Filename extensions are usually hidden in OS X, but if you find them useful, you can show them. If filenames are showing and you decide to hide them, OS X can still open the files with the proper apps.

When you rename a file or folder, don’t change its filename extension. If you change an extension, you may no longer be able to open the file with the app that was used to create it.

Many apps can safely convert a file from one type another. For example, TextEdit can convert a document from plain text format (.txt) to a rich text format (.rtf), and Preview can convert many types of graphics files.

For one file

  1. Select a file, then choose File > Get Info or press Command (⌘)–I.
  2. Click the triangle next to Name & Extension to expand the section and see the filename extension for the file.
  3. To show or hide the filename extension, select or deselect “Hide extension.”

For all files

  1. Choose Finder > Preferences, then click Advanced.
  2. Select or deselect “Show all filename extensions.”

Some filename extensions can’t be hidden. For example, images imported from a digital camera may continue to show the .jpg extension even after you deselect “Show all filename extensions.”

Published Date: Oct 20, 2015