There are a lot of reasons as to why you want to revert back to iOS 9 after installing iOS 10. It’s not difficult to revert, but you need to do it sooner than later.
Each version of iOS is signed (approved) by Apple. When iOS updates are released, the previous version remains signed for a short period of time. Eventually, Apple stops signing the previous version, which prevents you from installing the old version.
Here’s how to revert back to iOS 9.
First, you need to find a file called [iOS device].ipsw. If you are downgrading an iPhone,the file will have a name like, “iPhone8,2_9.3.5_13G36_Restore.ipsw”. Here’s how to find it.
In the Finder, hold down the Option key and select Go > Library. (The Library folder is usually invisible in your Home folder. If you don’t hold down the Option key, the Library selection will not be available.)
Open the iTunes folder.
Look for a Software Updates folder that corresponds to your device. So for iPhone, look for iPhone Software Updates and open it.
Look for a file called “[yourdevice]_9.3.5_[firmwarenumber]_Restore.ipsw” or something similar. This is the file that will allow you to revert back to iOS 9.
Drag that file to the Desktop.
Don’t see such a file? Search the Internet for
ipsw download. A few websites (such as IPSW Downloads) will have the old iOS software available. Download the appropriate .ipsw file (“[yourdevice]_9.3.5_[firmwarenumber]_Restore.ipsw”) and save it to your Desktop.
Install iOS 9
Connect your iOS device to your Mac using the sync cable.
Click on the device icon in the upper left.
Click on the Summary tab in the left column.
In the main window, click on the Restore iPhone button while holding down the Option key.
You may get an alert that says you need to turn off Find My iPhone/iPad/iPod. You can do this on the device by going to the Setting apps and then iCloud > Find My iPhone/iPad/iPod. After that, repeat step 5.
A navigation window appears. Navigate to the .ipsw file on your Desktop, select it, and click Open.
You’ll be asked to confirm. Click the Restore button to continue.
It takes a few minutes for iTunes to do its job, and soon you’ll have an iOS device running iOS 9.
This story, "How to downgrade back to iOS 9 if you don't like iOS 10" was originally published by Macworld.