Apple strictly controls what software can be installed on the iPhone and iPad in a way that you don’t see on your Mac desktops. 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, the software must be signed by Apple. This means that no other operating systems such as Android or Linux can 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 through online verification 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 period of time that the old version can still be installed before the company stops signing it altogether.
The signing window is a temporary period of time during which the software can be installed. As long as a particular version of iOS is being signed by Apple, it can be installed on your iPhone using the Settings > General > Software Update menu, Finder on macOS, or iTunes for Windows (and older versions of Apple’s desktop operating system).
This means that it is technically possible to downgrade iOS, but only for a very short period of time. You can do this using the IPSW file and recovery mode with a Mac or PC as long as Apple continues to sign the software. It is not possible to do this on the device directly.
After you have passed the signing window, the previous version of the software will no longer be available for installation. The only way to update the software on your device is to install the newest, actively signed version. This prevents iPhone and iPad owners from installing earlier versions of iOS and iPadOS, even if they have the IPSW software file stored locally.
This process is good for security
One of the main benefits of Apple’s restrictive operating system policy is that it prevents people from installing versions of iOS and iPadOS that have known vulnerabilities. By fixing these flaws in new software releases, Apple can effectively eliminate threats posed by outdated software.
It’s worth noting that this only works if you regularly update your device. You can leave the buggy version of iOS on your iPhone for as long as it takes to install the update, and your device will be at risk until you do. But once you have installed a new version of iOS, you cannot go back to a previous version.
The signing window gives Apple a fair amount of control over newly discovered exploits, as 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 signed and anyone upgrading from previous versions stumbled upon the fixed version thanks to Apple’s system.
It also helps Apple fight jailbreak
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 circumventing Apple’s restrictions by exploiting vulnerabilities to execute custom code. Once jailbroken, an iPhone or iPad can be used in a myriad of ways that Apple prohibits.
This includes installing prohibited apps like torrent clients, downloading software from legitimate and not-so-legitimate sources, and making changes to the way Apple operating systems work. It should come as no surprise that Apple actively fights 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 earlier versions of software that were successfully jailbroken. Many jailbreak advocates encourage those who want to jailbreak their devices not to update to the latest version of Apple’s operating system in an attempt to take advantage of jailbreak loopholes in older software that Apple has closed in newer versions.
While the push to upgrade may seem like an anti-consumer move, Apple has legitimate reasons to close these loopholes from a security standpoint. Since jailbreaking removes Apple’s restrictions by giving the user root or administrator 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 bypass 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 move forward in terms of software version (without the option to go back) has broader benefits for Apple and its ecosystem. Apple still issues some security updates for older versions of its operating systems, even those that are deprecated, but these are for the benefit of older devices that don’t support the latest versions.
New features arrive with new versions of the operating system, giving you an incentive to upgrade. You’ve probably noticed how often Apple reminds you when updates are available and even offers to install the update (although this requires consent in terms of entering your passcode).
By locking out users 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 can’t downgrade to a version that their app doesn’t support.
Apple publishes iOS usage statistics on its Apple Developer website. As of this writing in September 2022, 89% of iPhone devices introduced in the last 4 years were running iOS 15. 82% of all devices had moved to iOS 15.
A perfect system? Not quite
Blocking users of older versions of the operating system has great benefits in terms of security and development, but it is not a perfect system. Many applications have fallen by the wayside and have been lost due to the changes made in the new versions of iOS. One notable example is when Apple stopped supporting 32-bit apps with the arrival of iOS 11 in 2017.
This steady march forward relies heavily 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 that it will work on your iPhone 13. You also can’t downgrade your device to be able to play it.
Some users also complain that new versions of iOS hurt performance, mainly on older devices. After the signature window has closed, you’re stuck. The result is that you’ll get security updates, better website compatibility thanks to a newer version of Safari, and all the other benefits that come with a major iOS update.
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