How to Install the macOS 27 Beta on a Separate Volume (Without Risking Your Mac)

Installing a macOS beta on your main system is risky: some apps may stop working and you cannot easily go back. The safest solution is to install the beta on a separate APFS volume on the same disk. You then choose at startup which macOS to use, and your main system stays untouched.

Before you start

• Check that your Mac supports macOS 27: macOS 27 compatible Macs.
• Make a Time Machine backup.
• Keep at least 40 GB of free space.

Step 1: Create a new APFS volume

1. Open Disk Utility (Applications > Utilities).
2. Select your main container in the sidebar (usually "Macintosh HD" container).
3. Click + (Add APFS Volume), name it for example macOS Beta, format APFS, and click Add.

An APFS volume shares the free space of the disk: no need to choose a fixed size.

Step 2: Get the beta installer

1. Open System Settings > General > Software Update.
2. Click the (i) next to Beta Updates and choose macOS 27 Developer Beta or Public Beta.
3. When the update appears, do not click "Update Now" on your main system. Instead, get the full beta installer app ("Install macOS 27 beta"). Apple's developer and beta websites explain how to download it for your enrolled account.

Step 3: Install on the new volume

1. Open the installer.
2. When it asks for the destination, click Show All Disks and choose macOS Beta.
3. Follow the steps. The Mac restarts several times.
4. Set up the beta like a new Mac, or import data from your main volume with Migration Assistant.

Step 4: Switch between macOS versions

• Apple silicon: shut down, then hold the power button until "Loading startup options". Choose the volume.
• Intel: hold Option at startup and choose the volume.
• Or in System Settings > General > Startup Disk.

Removing the beta

Start on your main system, open Disk Utility, select the beta volume and click − (Delete Volume). The space is returned immediately.

If something goes wrong

If the Mac no longer starts at all, a DFU revive can reinstall the firmware without erasing data: revive or restore a Mac in DFU mode. macOS firmware files (UniversalMac IPSW) are on our Mac firmware page and in beta firmware.

Official reference: Apple: Use more than one version of macOS on Mac.