For the first time, anyone can install an Apple beta software upgrade without being a developer. In the past, only developers have access to beta iOS upgrades but right now, there’s a public beta for iOS 9 you might want to try out.
Although this upgrade is out for anyone to install, it doesn’t really mean that it’s ready to be used. As a matter of fact, you’re strongly advised not to install it on your primary device. Don’t install it on the device you use from day to day as things may go wrong and your apps may not really work the way they should.
There’ll be bugs. You should know that.
How to get started
1. First, go to Apple’s Beta Software Program page and Sign Up.
2. Sign in with your Apple ID, preferably the same Apple ID you use on your device (if you have multiple accounts).
3. Accept the terms and conditions when you’re done reading through.
4. Connect your phone to iTunes and make sure you backup. Don’t just rely on iCloud backup, be sure you have a local backup done through iTunes
5. Launch Safari on your iOS device and visit beta.apple.com/profile. Login with your Apple ID if you’re prompted and scroll down to step 2 (Download Profile) to download the needed configuration profile to your device.
6. Choose to install the profile and enter your PIN if asked. After installing the profile, restart your device.
7. Restarted? Now go to Settings > General > Software Update. My iPhone 4s was already trying to download the update because I was connected to a WiFi.
The update is almost finished. Just click Install Now and wait till the whole thing is done.
The whole point of downloading a public beta is to give your feedback to Apple and when you’re done installing the upgrade, you should see a new Feedback application on the springboard. Some of your apps may not work correctly and this should be expected. A beta software is an unfinished software, it is a work in progress.
No prompt to install iOS 9 after profile download?
In case you didn’t get the prompt to install iOS 9 after you’ve downloaded the beta profile, there could be two explanations:
1. You’re running an iOS version lower than iOS 8.1.3
2. Your device is jailbroken.
I didn’t get it the first time because I was running a jailbroken iOS 8.1. I had to restore iOS 8.4 without jailbreak before I could go to iOS 9 Public Beta 1.