Apple today released the first public beta of iOS 12 for compatible iPhone, iPad, and iPod touch models, enabling users who aren't signed up for the Apple Developer Program to test the software update ahead of its official release in the fall.
While iOS 12 introduces several new features, it is designed to work on all iPhone, iPad, and iPod touch models that can run iOS 11, and the company says it has focused on bringing performance improvements to both old and new devices.
That said, iOS 12 is pre-release software, so installing the Public Beta on a secondary device is highly recommended. The stability of beta software cannot be guaranteed, as it often contains bugs and issues that have yet to be ironed out, so installing it on your day-to-day device isn't advised.
Installing the Public Beta shouldn't take longer than half an hour, but first you should create a backup of your device's contents and settings. The following step-by-step instructions are given for iPhone, but apply to iPad and iPod touch just the same.
How to Create a Backup of Your Device in iTunes
Connect your iOS device to a Mac or PC using a Lightning to USB cable.
Click the device's icon in the top-left menu.
Under Backups, click This computer.
Tick the Encrypt iPhone backup checkbox if you want to back up your login credentials and any Health and HomeKit data.
Click Back Up Now.
Click iTunes -> Preferences… in the macOS menu bar.
Click the Devices tab.
Right-click (or Ctrl-click) the new backup, and select Archive from the contextual dropdown menu.
How to Enroll in the Apple Beta Software Program
Now that you've backed up your device, you're ready to download the iOS 12 Public Beta. To do so, you must enroll your iPhone, iPad, or iPod touch in the free Apple Beta Software Program.