This is how to delete useless languages on your Mac

What are language files?

Almost every application on your Mac is available in more than a dozen languages and thus contains specific language files for that matter. Since you don’t speak most of these languages, such files just waste space on your Mac and can be safely removed.

How to clear out unnecessary language files manually

Language files are kept in package contents of applications you have installed on your Mac. You can find them if you open the Resources folder and find folders ending with “.lproj”. Every folder contains language files for one particular language and thus has a name of this language or its shortening. For instance, here are the language files of Skype.

Language files in folder

In most cases, you can trash the folders and files for languages you don’t know or don’t speak. Note, that for every application you should manually find and select these files for removal. But, we know a way that's a bit easier.…

How to remove languages you don't use automatically

Instead of trashing language files manually for every single application, you can use CleanMyMac X to take care of it for you. 
Just download the application, launch it, and then hit Scan.

Smart scan

When the scan is over, click Run. This will clean up your Mac from various system and application junk including unwanted language files.

CleanMyMac X - System junk scan complete

Alternatively, you can proceed to the System Junk module, click Review Details and uncheck everything except Language Files. Moreover, you can manually edit the list of languages you want to be excluded from your system.

CleanMyMac X - Language files in System Junk module

After you have done it, click Clean then to exclusively delete language packs for more space on a Mac.

Download CleanMyMac X to safely delete language files from your Mac, and free up disk space for more important files.

Laptop with CleanMyMac
CleanMyMac X

Your Mac. As good as new.