Changing the default applications that opens when opening a file in Mac OS X is a definite must know, and can save you time as well as a headache.

Maybe you’ve downloaded a new app that you want to set as the default, or opening a picture could default to an app that takes a long time to load, such as Photoshop.


Change Default Application by Extension

default open with app

Change Default App extension

For this example I’ll change default video player from QuickTime to MPlayerX. Unfortunately there is no way to just set MPlayerX to just be the default player for all video files and their respective extensions. It has to be done, extension by extension.

First thing you’re going to want to do is find a file that has the extension that you want to change the default application for.

All you need to do to change the default application is:

  1. Right-click (control-click) on a file with the extension that you are wanting to change.
  2. Select “Get Info”
  3. Located “Open with:”
  4. Choose your desired default application.

Now a choice, do you want to change the file association for just this file, or do you want to change the file association for all files with this extensions?

  •  To apply it across all files with that extension make sure you click “Change All…”


Tips to make the process simpler

You may be thinking that the above is tedious, and truthfully it is. I’d like to see a better way of managing the default application, however until then here are some:

More Tips:

By default on Mac common filename extensions are hidden in Finder. To show all filename extensions:

  1. Open Finder
  2. From the menu bar select Finder -> Preferences
  3. Click the “Advanced” tab
  4. Enable “Show all filename extensions”

Even after you’ve changed the default application that opens you can still override the setting and choose another app.

  1. Right-click file
  2. Choose “Open With”

Your desired app not listed?

  1. If your desired app isn’t listed in the “Get Info” window, then choose “Other…”
  2. Navigate to the applications location (usually the Applications folder) and select it.
  3. Click Add.


Even More Tips:

Find a new (or better) application by file extension.

  1. Right-click file -> Get info -> and select “Open with:”
  2. Select App Store
  • This will show application in the Mac App Store that can be used with that specific extension.
  • It’s a great way to find new and sometimes better applications.

Not all applications require these methods.

  • Some apps are awesome enough to give you the choice of which extensions you want them to be associated with by default. If you want to set a new app to be the default, always check to preferences first.