When considering an upgrade, it is important to check if your device is capable of running the new iOS. Apple publishes a list of compatible devices with each new iOS version. Older devices not on the list can not run the new iOS.
According to Apple, the iOS 10 software can be used on the following devices.
• iPhone 7
• iPhone 7 Plus
• iPhone 6s
• iPhone 6s Plus
• iPhone 6
• iPhone 6 Plus
• iPhone SE
• iPhone 5s
• iPhone 5c
• iPhone 5
• iPad Pro 12.9-inch
• iPad Pro 9.7-inch
• iPad Air 2
• iPad Air
• iPad 4th generation
• iPad mini 4
• iPad mini 3
• iPad mini 2
• iPod touch 6th generation
Should I Upgrade My iOS?
Generally, the newer model devices will run the new iOS without any issues. However, things get a little more unpredictable for older model devices near the bottom of the list. While these devices may technically be able to run the new iOS, their performance may suffer because they have older processors and less RAM than the newer devices. The performance decrease could be minimal and some people may see no difference in speed or responsiveness while others may notice their device appears to run slower or feel sluggish.
Apple tries to ensure the best user experience possible when determining which devices are compatible with a new iOS. However, it is difficult to predict how an old device will handle a new iOS version. If there is a noticeable decrease in speed, this is typically evident regardless of which app you are using. Things like opening and closing apps may take a fraction of a second longer. App responsiveness when using an app may seem a bit slower than it was. The impact generally isn’t significant, but it can be noticeable.
For what it’s worth, I upgraded my old iPhone 5 to iOS 10 and so far it seems to be running fine. Your mileage may vary.
It is a good practice to backup your device before upgrading just in case something goes wrong with the upgrade. This article from the Apple website provides more information about backing up your device.
What Can I Do If the New iOS Isn’t Working Right?
Typically you will not have an issue when upgrading the iOS on your iPhone or iPad. If something doesn’t seem right after upgrading, you can try restoring the device to reinstall the new iOS. A fresh installation of the iOS may resolve the issue. This article from the Apple website explains how to restore your device. Restoring the backup you made prior to beginning the upgrade will reinstall all your data on your device.
Can I Go Back to the iOS 9 If I Don’t Like iOS 10?
In most cases, the answer is No.
When you install any iOS version on your device, it will check with Apple servers to get a digital signature. This is basically a check to make sure the iOS is the latest approved version by Apple. There is only a short period of time from when a new iOS version is released that Apple continues to sign the older iOS. When Apple stops signing iOS 9.3.5, you will no longer be able to downgrade from iOS 10 to iOS 9 on your device. If you think you may want to downgrade from iOS 10 to iOS 9, you will need to move quickly.
The downgrade process is more involved than simply tapping a Downgrade button. Instead, you need to download an IPSW file of the old iOS version for your device that is still being signed. An IPSW file is the iOS software file for a specific device. You must then use iTunes on your computer to load the IPSW file to your device. There are many articles on the Internet describing the downgrade process. While it isn’t difficult to downgrade the iOS, it isn’t something everyone will want to attempt.
Typically you won’t have an issue when upgrading a fairly new iPhone or iPad model. It is the oldest models on the iOS device compatibility list that could potentially suffer a performance decrease. You will need to weight the advantages and new features of the new iOS to determine if it is worthwhile upgrading an older device.