Why is the "Encrypted" format not available in the list when erasing a USB flash chip in Disk Utility?

It shows up for normal, external hard disk drives. Is there a way I can force it to encrypt?

The installed OS X is El Capitan.

Solution 1:

You can't do it from Disk Utility but you can do it from Finder by right-clicking on the partition and choosing Encrypt.

1. Open Disk Utility and click on the drive (not the partition)

2. Click Erase button

3. Choose Name

4. Choose Format: OS X Extended (Journaled)

5. Choose Scheme: GUID Partition Map

6. Click Erase button

7. When complete, open Finder

8. Right-click on the new drive partition

9. Select Encrypt

10. Enter passwords

11. Finish

Solution 2:

1. Open Disk Utility
2. In the top left of the Window, select the View drop down
3. Select Show All Devices
4. Click on the top level external drive (Note in the image below in the sidebar how the parent device is selected)
5. Press the Erase button and set the Scheme to GUID Partition Map

At this point, the Format option will contain the encryption options:

Solution 3:

For newer versions of Mac OS (Big Sur and onward), Mac OS Extended (Journaled, Encrypted) is no longer an option. If you erase it unencrypted and then use Disk Utility to encrypt, it gets converted to an APFS file system.

Previously, I would always use Mac OS Extended (Journaled, Encrypted) for Time Machine backups. Big Sur added Time Machine support for APFS (Encrypted).