On the Mac, a lot of programs hide the .zzz extension by default. Is there a way to turn this behaviour off so that extensions are never hidden by default?

I know I don't actually need it, I just prefer it to be there.

2 Answers 2


With Finder active, hit Cmd+, to go to preferences. In the advanced section, you will find the option to show file extensions.

  • great! it works
    – Joey
    Dec 14, 2016 at 5:35

AppleShowAllExtensions controls this behavior. It defaults to 0 (false). Read the value by entering this in a terminal:

defaults read -g AppleShowAllExtensions

Set it to 1 (true) by entering the following in a terminal:

defaults write -g AppleShowAllExtensions -bool TRUE

To also restart the Finder so that the change takes effect immediately (rather than after restarting / logging out & back in):

defaults write -g AppleShowAllExtensions -bool TRUE && killall Finder

To reset to the default value (and restart the Finder):

defaults delete -g AppleShowAllExtensions && killall Finder


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