Every app on a Mac ships with dozens of language localizations you will never use. On a small 128 or 256 GB drive, removing them frees real space.
Short answer: use the free Monolingual utility to strip unused languages from installed apps and macOS itself, and never delete English even if you use another language.
Why the files pile up
Major apps — Word, Photoshop, Chrome, Slack — include menus and resource files for 30-40 languages. macOS itself ships a long list of system dictionaries.
Across a fully used Mac, those localizations sum to 1-3 GB of pure waste for anyone who only uses one or two languages.
Using Monolingual safely
- download Monolingual from its official site
- open it — you see a long list of languages
- check every language you do not use
- leave your primary language unchecked
- leave English unchecked even if it is not your primary language
- click Remove
Monolingual scans every installed app's package contents and removes the unused localization bundles.
Why English stays
macOS and most third-party apps fall back on English strings when a localization is missing or fails to load. Removing English can crash apps that assume it is there — the typical failure mode is an app that refuses to launch.
Run Monolingual once when you first set up a new Mac, and once every few major macOS upgrades. Daily cleanup is not needed.
Better next routes
If you want the broader Mac cleanup framing, continue with How to Find Large Hidden Files on Mac.
For the deeper desktop context, use the desktop cleanup FAQ.