Deleting language files on Mac: why it is a bad idea now

Part of: What can I safely delete on my Mac? Safe, risky and never (Safe to delete)

Do not delete language files from your apps. It used to be a popular trick, but on a modern Mac it saves little, it can break an app, and the files come back with the next update. There are safer ways to free space.

What language files are

Mac apps carry text and images for many languages. Each language sits in a folder inside the app, ending in .lproj, such as de.lproj. The app shows the language you picked in System Settings and ignores the rest.

You can see this for an app on your Mac. This only reads:

ls /Applications/Safari.app/Contents/Resources | grep -c lproj

It counts the language folders in that app. Apps like Safari ship dozens of them.

It looks like wasted space, which is why people wanted to remove it.

Why it is a bad idea now

Apps are signed. A developer signs an app, and the signature covers the files inside it. macOS checks the signature when the app runs and when it updates. If a file inside the app changes or goes missing, the check can fail. The app can then be flagged as damaged or refuse to open.

You can see the check yourself. This command only verifies, it does not change anything:

codesign --verify --deep --strict --verbose=2 /Applications/Safari.app

When the app is intact it ends with “valid on disk” and “satisfies its Designated Requirement”. Removing language files is exactly the kind of change that can turn that into a failure.

System apps are sealed. macOS itself sits on a sealed, read-only volume, so the built-in apps cannot be changed in a normal way. You can confirm it with:

mount | grep ' on / '

The line includes “sealed” and “read-only”. This is deliberate, and it is a good reason to leave system apps alone.

Updates undo it. When an app updates, it puts its language files back. Any work you did is lost, and the update can fail if the app has been changed.

The gain is small. Language files are a small part of an app compared with its code and data. Caches, old installers and unused apps are much bigger and much safer to review.

What breaks if you do it

• The app can show a damaged or unverified warning.
• It can refuse to open until you reinstall it.
• A later update can fail or reinstall the files.
• If you switch your Mac’s language later, the app may show mixed or missing text.

None of this is dramatic, but it costs more time than the space is worth.

The Safe / Risky / Never box

What to do instead

1. Remove apps you no longer use. This frees the whole app, language files included. See App leftovers on a Mac for what an uninstall can leave behind.
2. Clear large caches. See Is it safe to delete ~/Library/Caches?.
3. Look at the biggest folders first. Find what is large before you try to shave small items. What can I safely delete on my Mac? gives a Safe, Risky and Never label to the common ones.
4. Check your free space with df -h / after each step, so you know it worked.

Common mistakes

• Trusting a tool that promises to “slim” apps. If it edits files inside an app, it carries the same risk as doing it by hand.
• Starting with system apps. They are on a sealed volume. Changes there are blocked, or they break the system’s checks.
• Counting the saving before checking. Look at how large the app is and how large its language folders are. For most apps it is not worth the risk.

Quick checklist

1. Leave language files alone.
2. Remove apps you have not opened in a long time.
3. Review caches and downloads.
4. Check free space with df -h / after each step.

Find the big things first

DiskJoy is our product. It scans your disk and shows reclaimable space by category. It is read-only today, and cleanup is not available yet. The scan can show where the large items are on your Mac, so you can skip small ones like language files.