MacOS – How to hide all file extensions in subdirectories of a given folder

The "Show all filename extensions" option overrides the "Hide extension" option in Get Info. This means that there are a few possible solutions one could try to find in order to hide ".app" extensions while showing the rest:

1. Find a way to exclude certain extensions from "Show all filename extensions".
2. Find a way to hide extensions, other than the "Hide extension" option, that it is not affected by the "Show all filename extensions" option.
3. Find a way to override the "Hide extension" option, other than the "Show all filename extensions" option, that can be configured to include or exclude items based on their extensions, or perhaps even by their location (e.g. exclude the Applications folder).

To the best of my knowledge, none of these are possible, but I would be happy to be proven wrong about that.

Possible Workaround

The easiest workaround I can think of is to leave "Show all filename extensions" unchecked and to manually set other files to explicitly show their extensions, which can be done very easily with Automator and the SetFile command.

You can set this up as either a service or an application. In both cases, it can be used on both files and folders, and will also process the contents of subfolders.

To set this up in Automator, add a "Run Shell Script" action, set "Pass input" to "as arguments" and set the script to this:

(Note: You have to install Xcode to get the SetFile command.)

for f in "$@"
do
    find "$f" -name "*.*" -exec SetFile -a e {} \;
done

If you set this up as a service, be sure to change "Service receives selected" to "files or folders".

You could also look into using this as a folder action. As files are added to a folder, the script will automatically set their extensions to be shown. For example, it could be useful to attach such a folder action to Downloads, Documents and the Desktop, or any other folder which frequently receives files with "Hide extension" checked.

Hopefully, setting this up as a service would make it so trivial to use that you wouldn't even need to worry about batch-processing an entire volume (which could take awhile). Rather, you could simply use it as needed whenever you come across files or folders of files with hidden extensions.

There is not a safe and advisable way to achieve what you are after because this function of the OS is controlled by the Launch Services database. Developers register the filetypes their applications support with the OS on first launch.

The best way to get this fixed is to petition the developer to add support for the file extension in a future version of their application.

With that said you have already found the only documented way that Apple offers for overriding the edicts of the Launch Services database. If you want to dig deeper and take the road less traveled supported here are a few pointers.

There is a .plist file that governs part of what Launch Services does located at: ~/Library/Preferences/com.apple.LaunchServices.plist

Apple notes that removing this plist can clear out unwanted Open With contextual menu options. But that's the opposite of what you're after.

It's a binary .plist but you could convert it to an xml version and experiment a little to see if you can come up with a recipe to achieve what you're after. This isn't advisable, it could cause harm, and it will most likely get overwritten by the OS at some point.

There is also a tool hidden a bit deeper in the OS called lsregister which could be helpful in exploring Launch Services's plumbing. Here is a helpful explanation of lsregister and its options.