Mac storage basics · Apps and macOS itself
Can I remove unused languages from Mac apps to save space?
Short answer: Not any more — removing files inside signed apps can break their code signature and stop them opening, and updates restore them anyway. The space saved is small.
It's not a good idea any more. Modern Mac apps are code-signed, and deleting files inside them — such as language folders — can break the signature, so the app may refuse to open or be flagged as damaged. App updates would also put the files back.
The space involved is small compared with caches, media and old backups, so focus there instead.