macOS can lock a Mac folder’s contents inside an AES-encrypted disk image that requires a password before the files can be opened.
A normal Finder folder has no password box. For anyone figuring out how to put a password on a Mac folder, Disk Utility supplies the built-in solution: convert the folder into an encrypted disk image, verify the copied files, then eject the image so the contents are locked.
The original folder does not become encrypted during this process. Keep it until you confirm the disk image opens correctly, then remove the unprotected original if you no longer need it.
How Do You Password-Protect An Existing Mac Folder?
Disk Utility can turn an existing folder into an encrypted disk image while keeping the files together. Apple’s current Disk Utility instructions for macOS Tahoe 26 use File > New Image > Image from Folder for this job.
- Open Disk Utility. In Finder, open Applications > Utilities > Disk Utility.
- Choose File > New Image > Image from Folder.
- Select the folder you want to protect, then click Open.
- Enter a filename for the disk image and choose where to save it.
- Open the Encryption menu and choose 256-bit AES encryption. Apple also supports 128-bit AES encryption; the 256-bit option uses the higher bit count.
- Enter the password twice when prompted, then click Choose.
- Open Image Format and choose RAW Image if you want to add, remove, or edit files after mounting the image.
- Click Save, then click Done.
Disk Utility creates the image and mounts it in Finder. Open a few files to confirm they copied correctly, then eject the mounted image; the encrypted container is now closed.
Opening, Editing, And Locking The Files Again
An encrypted disk image behaves like a mounted drive after you enter its password. Finder shows the mounted image in the sidebar and lets you work with its files until you eject it.
- To open it, double-click the saved disk image and enter its password.
- To edit files, open the mounted image in Finder and work inside that mounted volume.
- To lock the contents again, eject the image from Finder after closing any files that are still open.
- To move the protected collection, copy the disk-image file itself rather than the mounted volume.
Ejecting matters because Apple states that anyone with access to the Mac can use the documents while the secure disk image remains mounted. The password protects the image when it is closed; it is not a second lock screen around files that are already mounted.
Disk Utility Choices That Change The Result
Disk Utility’s encryption and image-format choices control how the protected container behaves later. The settings below keep an existing folder editable without turning the whole Mac into a locked volume.
| Disk Utility Choice | Setting To Use | What It Does |
|---|---|---|
| Source | Image from Folder | Copies the selected folder into a disk image |
| Encryption | 256-bit AES encryption | Uses Apple’s documented 256-bit AES option |
| Other encryption | 128-bit AES encryption | Uses Apple’s documented 128-bit AES option |
| Editable image | RAW Image | Allows files to be added, removed, or edited after mounting |
| Read-only archive | Read-only image | Prevents changes to the image contents after creation |
| Smaller archive | Read-only Compressed | Compresses a read-only copy of the folder |
| Finished session | Eject in Finder | Unmounts the image so its contents are no longer open in Finder |
| Original folder | Remove only after testing | Avoids deleting the only working copy before verification |
Which Disk Image Format Should You Choose?
RAW Image is the useful choice when you expect to reopen the encrypted disk image and edit its contents. A read-only image fits records you want to preserve without later changes, while a compressed read-only image favors storage space over editability.
Apple’s Disk Utility disk-image instructions also describe blank encrypted images. A blank image works well when you want an encrypted container first and plan to add files over time rather than converting one finished folder.
For a blank image on a Mac using macOS 10.13 or later, Apple recommends APFS or APFS (Case-sensitive). Apple Sparse Image (ASIF) is another current image format; it grows with the data stored inside instead of reserving its full capacity at creation.
Common Folder-Password Problems And Fixes
Mac folder password problems usually come from leaving the original folder exposed, choosing a read-only format, or forgetting to eject the image. The table below maps each symptom to the action that fixes it.
| What You See | Likely Cause | What To Do |
|---|---|---|
| No password prompt | The image may still be mounted or its password may be stored in Keychain | Eject it; if it still opens automatically, check whether Keychain is supplying the password |
| Files are still visible outside the image | The original folder still exists | Verify the encrypted copy, then remove the original if appropriate |
| You cannot edit files | A read-only image format was selected | Create a new image using RAW Image |
| The password is rejected | The password was typed differently | Check case and keyboard layout; a forgotten image password blocks access to the files |
| The image will not eject | A file inside it is still open | Close the file or app using it, then eject again |
| You want the whole Mac protected | A folder image is too narrow | Use FileVault for startup-disk encryption |
| You only changed Finder permissions | Permissions are not a folder password | Use an encrypted disk image when a password prompt is required |
FileVault Solves A Different Problem
FileVault encrypts the Mac startup disk rather than adding a separate password to one Finder folder. FileVault fits when the goal is protecting everything on the Mac if the computer is lost, stolen, or accessed before login.
For a small set of private files, an encrypted disk image is more targeted. You can copy that image to another drive or storage service while keeping its contents encrypted, and you only mount it when you need the files.
Lock The Files, Then Eject The Image
An encrypted Mac folder stays protected only after its disk image is ejected and the unencrypted original is no longer exposed. Create the image, test it before deleting anything, and eject it whenever the files are not in use.
- Convert the folder with File > New Image > Image from Folder.
- Choose 256-bit AES encryption and set a password you can retain securely.
- Use RAW Image if the contents need to remain editable.
- Open the finished image and verify several files before removing the original folder.
- Close open documents and eject the mounted image after every session.
After ejection, opening the encrypted disk image asks for its password unless that password is stored in Keychain for your account. Leave Keychain storage off on a shared Mac when you want the prompt to appear on every open.
References & Sources
- Apple.“Create a disk image using Disk Utility on Mac.”Documents current macOS Tahoe 26 steps for encrypted images created from folders and blank images.