Default apps/urls/extensions/utis settings on Monterey

Although I set Microsoft Outlook as my default mail app, links to .eml files were still being opened in Mail.
This may have been there a while, but I just stumbled upon the settings in Default Apps in System Preferences. Here you can change the app associated with a file extension, change the default app for URLs. There’s even a section for Urinary Tract Infections.

Haha. What is it really?

Actually, RCDefaultApp is a third party preference pane – it is not part of macOS standard installations. You probably added RCDefaultApp to some version of OS X/macOS once.


Couple of thoughts:

  1. Default mail app is what you use when you click a link to send email.
    However opening eml files follows the standard app for this file format. I believe same idea for Default browser and HTML files.

  2. You can have an easier shortcut, when you right click the file format then Get info > Open with. From here choose the application you want to use to open the file one time, or click Change All to set it as the default app for this extension.

Ah ha!
Mystery solved. Thanks RCDefaultApp!

UTIs explained

And the other kind

There is a newer version that you may want to use if/when RCDefaultApp stops working for you. This one is written in Swift:


Unfortunately, it looks like SwiftDefaultApps doesn’t have the Extensions pane; one of my main uses.

What a strange omission.