Why a separate volume rather than a partition
APFS containers share free space between the volumes inside them, so a new volume does not take a fixed slice of your drive the way a traditional partition would. It grows as the beta install needs room and gives the space back when you delete it.
That means you do not have to decide in advance how much room to allocate, and you do not have to repartition — a process that on older filesystems was slow and occasionally destructive. Creating and deleting an APFS volume takes seconds and touches nothing else.
Creating the volume
Open Disk Utility, select the container that holds Macintosh HD in the sidebar — the container, not the volume inside it — and click the + button above the volume list. Name it something obvious like "macOS Beta" and leave the format as APFS.
Do not set a reserve or quota size unless you have a specific reason. Leaving both blank is what allows the volume to share free space with your existing system, which is the entire advantage of doing it this way.
Installing the beta onto it
Enrol your Apple Account at beta.apple.com or developer.apple.com, then open System Settings → General → Software Update → Beta Updates on your stable system and select the macOS beta channel. Start the download, and when the installer launches, click Show All Disks and choose the new volume as the destination.
That last step is the one that matters. Accepting the default target will install the beta over your working system, which is precisely what you set out to avoid. Read the destination screen carefully before continuing.
Switching between the two systems
Hold the power button at startup on an Apple silicon Mac to reach the startup options screen, then pick the volume you want. System Settings → General → Startup Disk sets which one boots by default.
Both systems see the same drive and the same free space, but they have separate user accounts, applications and settings. iCloud will sync your data into the beta system if you sign in, which is usually what you want for realistic testing.
Removing it afterwards
When you are finished, boot into your stable system, open Disk Utility, select the beta volume and click the − button. The space returns to the container immediately and your main system is untouched.
That clean removal is why this method is worth the fifteen minutes it takes. There is no downgrade to perform, no restore from backup and no risk to the system you actually depend on — see our main-device guide for why the same option sadly does not exist on iPhone.
Frequently Asked Questions
Does installing macOS on a separate volume risk my main system?
No, provided you select the new volume as the install destination. The two systems are independent and share only free space.
How much space do I need for a macOS beta volume?
Around 40 GB free in the container. APFS volumes share free space, so you do not need to allocate a fixed size in advance.
How do I switch between the beta and my normal macOS?
Hold the power button at startup on Apple silicon to reach startup options and pick a volume. Startup Disk in System Settings sets the default.
How do I remove the beta volume later?
Boot into your stable system, open Disk Utility, select the beta volume and click the − button. The space returns immediately.