How to upgrade to iOS 9 (and, if you need to, reinstall iOS 8)
But then, if, for whatever reason, you decide you need to downgrade back to iOS 8, I’ll also show you how it’s done. Keep this in mind: The window to revert back is small. Apple will eventually stop authorizing iOS 8, and when that happens and you have iOS 9 installed, there’s no going back.
If you’re very concerned about your apps not working or your device not performing up to par, don’t upgrade to iOS 9 immediately. You’d be better off waiting for Apple to release the first major update to iOS 9, which may address some of the bugs you are afraid of running into, and it also gives developers time to update their apps.
Apple says that iOS 9 is compatible with the following devices:
Some features in iOS 9 may not work on older devices in the list above. If you’re an owner of a device that’s on the older side of the compatibility list, consider putting off the upgrade to iOS 9 until you get more information on how the new iOS performs on your device.
Before you upgrade to iOS 9 (and, when iOS 9 is installed, before you install any iOS updates), you need to back up the data on your device. You can back up via iTunes on your Mac (fastest) or back up to iCloud (more convenient).
We have complete instructions on how to back up your iOS device in iTunes 12 or via iCloud. (The linked article is about preparing for iOS 9, but it includes backup instructions.)
OK, it’s time to install the new iOS. You have two ways to install iOS 9: Directly on your device using a wireless connection, or through iTunes with your device connected to your Mac. If you want to install directly, you need several free gigabytes of storage space available. If you don’ have to room, use iTunes on your Mac.
If you don’t see an alert, click on the device icon in the upper left and then click on the Summary tab in the left column. In the right window, click on the Check for Update button. If it’s available, the version of iOS 9 for your device will download to your computer for installation.
A new iOS can also mean a fresh new start. Maybe you’ve installed too many apps on your iOS device, and you want to use this opportunity to start from scratch and install only the apps you really want. Whatever the reason, you can wipe out your device and then install iOS 9.
This is done by restoring your iOS device using iTunes. It takes more time than just upgrading the already-installed operating system, and that doesn’t include the time it takes to reinstall your apps. Here’s how to restore and then install iOS 9 on your device.
If you restore as a new device, you’ll have to enter settings for Wi-Fi, your Apple ID, Siri, and more. You can then use iTunes to determine what apps to install on your device.
If you want to restore from a backup, you’ll be asked to select a backup file that iTunes will use to restore your device.
You installed iOS 9. Whoo-hoo! But then you noticed that your device is behaving badly. Boo! You want to revert back to iOS 8.
If that’s what you want to do, don’t hesitate. Apple “signs” each version of iOS, which is a way of approving the software for each device. When a new version is released, the previous version remains signed for a short period of time, and then Apple stops signing the previous version. This means you can’t go back to the old version. (If you waited, say, a week after iOS 9 was released, there’s a good possibility that Apple stopped signing iOS 8 and you can’t go back.)
To see if you can revert back to iOS 8, look for the .ipsw file on your Mac. Here’s how to find it.
If you don’t see a file, you can try searching the Internet for ipsw download. There are a few websites that have old software available.
Once you acknowledge that you have the ipsw file, here’s how to revert back to iOS 8.
iTunes will perform a restoration of your iOS device, and in a few minutes, iOS 8 will be up and running.