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How to

Lock a file so it can’t be changed

Select it in Finder, press ⌘I, and tick Locked — it can still be opened and copied but not changed or trashed without asking. chflags uchg does the same from Terminal.

Without Terminal

  1. Select the file in Finder.
  2. Press ⌘I.
  3. Tick Locked under General.

In one command

Lock a file:

chflags uchg contract-final.pdf

Unlock it again:

chflags nouchg contract-final.pdf
Or just ask Titan
Lock the final versions in my Contracts folder so nothing overwrites them. Do it with Titan

Titan is an AI that lives on your computer: tell it what you need and it does it while you watch — you press Return, nothing runs by itself. What is Titan?

Titan isn’t on this computer yet. Get Titan, then press the button again — the task will be waiting, typed in.

Related

Make a password-protected folderCopy a folder to a backup drive