How to Lock a Folder on Mac | Encrypt It With A Password

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Use Disk Utility to place Mac folder contents in an encrypted disk image; after you eject it, reopening the image requires its password.

A normal Finder folder does not ask for a separate password. If you need to know how to lock a folder on Mac, Disk Utility can copy that folder into an AES-encrypted disk image that stays protected when the image is not mounted.

The process takes a few menu choices, but one detail matters more than the rest: creating the encrypted image does not remove the original folder. Test the protected copy first, then remove the unprotected original if you no longer need it.

What Actually Protects A Mac Folder?

An encrypted disk image protects the files with its own password instead of relying only on your Mac login. Apple supports 128-bit and 256-bit AES encryption for disk images created with Disk Utility.

The image behaves like a removable drive while it is open. Files inside can be viewed or edited according to the image format, and they stay accessible to anyone using your Mac until you eject that mounted image.

  • Disk image closed: opening the protected contents requires the image password.
  • Disk image mounted: the files appear in Finder like files on another drive.
  • Original folder still present: those original files remain outside the encrypted image until you delete or move them.

Locking A Folder On Mac With Disk Utility

For an existing folder, Disk Utility can create an encrypted image directly from that folder. The current Apple procedure uses File > New Image > Image from Folder.

  1. Open Disk Utility. On current macOS, click the Apps icon in the Dock, type Disk Utility in the search field, then open Disk Utility.
  2. Choose File > New Image > Image from Folder.
  3. Select the folder you want to protect, then click Open.
  4. Enter a filename for the disk image and choose where to save it.
  5. Open the Encryption menu and choose an AES encryption option. For sensitive files, 256-bit AES encryption is the larger of Apple’s two supported key sizes.
  6. Enter and re-enter a password, then click Choose.
  7. Open Image Format. Choose RAW Image if you need to add, remove, or edit files later.
  8. Click Save, then click Done.

Disk Utility creates the image and mounts it automatically. A disk icon appears on the desktop and in the Finder sidebar, which confirms that the protected copy was created and opened.

Choose The Encryption And Image Format Carefully

Disk Utility supports both 128-bit and 256-bit AES encrypted disk images, while the image format decides whether the contents can change after creation. For a folder you plan to keep using, RAW Image is the practical choice because Apple lists it as editable.

Disk Utility Choice Recommended Setting What It Changes
Source Image from Folder Copies the selected folder into a disk image
Encryption 256-bit AES encryption Protects the image with the larger supported AES key size
Password A unique password you can retrieve later Required to access the encrypted image later
Image Format RAW Image Allows files inside the image to be added, removed, or edited
Save Location A folder you can find again Controls where the encrypted image file is stored
After Creation Eject the mounted image Stops the protected files from remaining openly accessible
Original Folder Remove only after testing Prevents an unencrypted duplicate from defeating the setup

Apple’s current Disk Utility disk-image instructions also list read-only and compressed read-only formats. Those fit archives that should not be edited, while a blank encrypted image can work better when you want an empty protected container that you will fill over time.

If you create a blank image instead, Apple recommends APFS or APFS (Case-sensitive) for an encrypted image used with a Mac on macOS 10.13 or later. Apple also warns that a forgotten disk-image password prevents access to the files inside.

How Do You Open And Lock It Again?

Opening the encrypted image means mounting it; protecting it again means ejecting it when you finish. The password does not hide files while the image remains mounted.

  1. In Finder, double-click the saved disk image.
  2. Enter the disk-image password when macOS requests it.
  3. Use the mounted volume in Finder to open, add, remove, or edit files if its format permits changes.
  4. When finished, find the mounted volume in the Finder sidebar and click the eject symbol beside its name.

The mounted volume disappears from Finder after ejection. The next time the encrypted image is opened, macOS must obtain its password again before the protected contents can be mounted.

Remove The Unprotected Copy After You Test The Image

The original folder is still ordinary Finder data after Disk Utility creates the encrypted image. Open several files from the image, confirm that anything you need is present, eject the image, then open it again with the password before removing the source folder.

If the test passes and you do not need the original, drag that folder to the Trash and choose Finder > Empty Trash. Copies in backups, cloud storage, external drives, or other folders are separate and must be handled on their own.

Mac Protection Method What It Protects Use It When
Encrypted image from a folder One copied folder’s contents You want a separate password for existing files
Blank encrypted disk image Files added to a new container You want a reusable protected storage area
RAW disk image An editable image You expect the contents to change
Read-only disk image A fixed image You want files viewable but not editable inside the image
Read-only compressed image A fixed compressed image You want a fixed image stored in compressed form
Finder permissions Access by Mac users and groups You need account-based access controls, not a separate folder password
FileVault The Mac startup disk You want whole-disk protection tied to Mac login security

Finish With A Password-Protected Folder Setup

The dependable setup is an encrypted image that has been tested, ejected, and separated from any unprotected duplicate. Use this sequence when the goal is a folder whose contents require a separate disk-image password.

  1. Create the encrypted image with Disk Utility > File > New Image > Image from Folder.
  2. Choose AES encryption and set a password you can retain.
  3. Use RAW Image when the files need to stay editable.
  4. Click Save and Done, then inspect several files inside the mounted image.
  5. Eject the image from Finder and open it again to verify password access.
  6. Only after that test, remove the original unencrypted folder if you no longer need it.
  7. Eject the image every time you finish using the protected files.

That last habit matters: encryption protects the disk image while it is closed, while an open mounted image behaves like a normal local volume for the signed-in Mac user. Anyone using that signed-in account can reach the mounted files until the image is ejected.

References & Sources

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