Apple tightly controls which software can be installed on the iPhone and iPad in a way not seen on its Mac desktop computers. So is Apple right to prevent you from installing older versions of iOS or iPadOS on a whim, or is this an example of corporate overreach?
New Software Must Be “Actively Signed” By Apple
To install software on the iPhone or iPad, software must be signed by Apple. This means that other operating systems like Android or Linux cannot be installed on Apple smartphones or tablets, only Apple-approved software.
In addition to this requirement, the software must be actively signed, which means that Apple must approve the installation using an online check before it can be installed on an iPhone. Apple will only actively sign software for a limited time. When a new version of iOS or iPadOS is released, there is only a short window of time where the previous version can still be installed before the company will stop signing it altogether.
The signing window is a temporary period of time during which software can be installed. For as long as Apple is signing a particular version of iOS, it can be installed on your iPhone using the Settings > General > Software Update menu, Finder on macOS, or iTunes for Windows (and earlier versions of Apple’s desktop OS).
This means that it is technically possible to downgrade iOS to the previous version, but only for a very short window of time. You can do this using the IPSW file and Recovery Mode with a Mac or PC for as long as Apple is still signing the software. It’s not possible to do this on the device directly.
After the signing window has passed, the older version of the software is no longer available for installation. The only way to update the software on your device is to install the newer, actively signed version. This bars iPhone and iPad owners from installing older versions of iOS and iPadOS, even if they have the IPSW software file stored locally.
This Process Is Good for Security
One of the major benefits of Apple’s restrictive operating system policy is that it prevents people from installing versions of iOS and iPadOS that have known exploits. By fixing these flaws in new versions of software, Apple can effectively remove threats posed by outdated software.
It’s worth keeping in mind that this only works if you regularly update your device. You’re free to leave the flawed version of iOS on your iPhone for as long as it takes you to install the update and your device will be at risk until you do. But once you’ve installed a new version of iOS, there’s no going back to a previous version.
The signing window gives Apple a good amount of control over newly discovered exploits, as was seen in August 2022 when Apple released iOS and iPadOS 15.6.1 to fix two “actively exploited” security vulnerabilities discovered in iOS 15.6. Within a week of release, iOS 15.6 was no longer being signed and anyone upgrading from previous versions was bumped onto the fixed release thanks to Apple’s system.
It Also Helps Apple Combat Jailbreaking
The other reason Apple is so keen on restricting which versions of iOS and iPadOS can be installed on an iPhone or iPad is to prevent jailbreaking. This is the act of evading Apple’s restrictions by exploiting vulnerabilities to run custom code. Once jailbroken, an iPhone or iPad can be used in a myriad of ways that Apple forbids.
This includes installing banned applications like torrent clients, sideloading software from legitimate and not-so-legitimate sources, and making changes to the way Apple’s operating systems work. It should come as no surprise that Apple actively fights against this practice, making it as difficult as possible for you to jailbreak your device.
By using an active signing window, Apple can prevent people from rolling back their devices to previous versions of software that were successfully jailbroken. Many jailbreaking advocates encourage those who want to jailbreak their devices not to update to the latest version of Apple’s operating system in a bid to take advantage of jailbreaking loopholes in old software that Apple has closed in newer releases.
While the pressure to update may seem like an anti-consumer move, Apple has legitimate reasons for closing these loopholes from a security standpoint. Since jailbreaking removes Apple’s restrictions by providing the user with root or admin-level permissions, removing the ability to downgrade to jailbreak protects your device from others.
For example, authorities could potentially exploit this ability to jailbreak your device and circumvent security measures to gain access to your device and the data stored on it. Removing the ability to jailbreak inconveniences a small percentage of users to benefit the vast majority of the ecosystem (from a security standpoint).
Apple Benefits in Other Ways
Having the ecosystem constantly moving forward in terms of software version (without the option of going backward) has broader benefits to Apple and its ecosystem. Apple still issues some security updates for past versions of its operating systems, even those that are deprecated, but these are for the benefit of older devices that do not support the latest versions.
New features arrive with new operating system versions, which provide an incentive for you to upgrade. You’ve likely noticed how often Apple reminds you when updates are available, and even offers to install the update (though this requires consent in terms of entering your passcode).
By locking users out of older versions of the operating system, Apple has less work to do in terms of maintaining compatibility across its range of services. It’s easier for Apple to maintain a consistent user experience across generations of devices once the option to downgrade is removed. Developers can target a minimum version of iOS, knowing that users cannot downgrade to a version that their app doesn’t support.
Apple publishes iOS usage statistics on its Apple Developer website. At the time of writing this article in September 2022, 89% of iPhone devices introduced in the last 4 years were using iOS 15. 82% of all devices in the wild had moved to iOS 15.
A Perfect System? Not Quite
Locking users out of old versions of the OS has big benefits in terms of security and development, but it’s not a perfect system. Many apps have fallen by the wayside and been lost due to changes made in new versions of iOS. A notable example is when Apple dropped support for 32-bit apps with the arrival of iOS 11 in 2017.
This constant march forward very much depends on software developers maintaining their apps, which is outside of Apple’s control. If you bought a game ten years ago on your iPhone 4S, there’s no guarantee it will work on your iPhone 13. You also can’t downgrade your device in order to play it.
Some users also complain that new versions of iOS harm performance, mostly on older devices. After the signing window has closed, you’re stuck. The upshot is that you’ll get security updates, better compatibility on websites thanks to a newer version of Safari, and all the other benefits that a major iOS upgrade brings.