Apple stopped signing iOS 18.6 on Thursday, just one week after releasing iOS 18.6.1 alongside watchOS 11.6.1 to enable the Blood Oxygen monitoring feature on Apple Watches that were previously barred from offering the feature to end users under an International Trade Commission ruling – but later circumvented by a U.S. Customs and Border Protection ruling that patent troll Masimo is now once again suing over.
By unsigning iOS 18.6, Apple has configured its software update servers to reject any restore requests made by end users to install this particular firmware version, instead pushing them to install a newer version. At the time of this writing, both iOS 18.6.1 and the newer iOS 18.6.2 update that Apple released this week are still being signed as viable restorable versions of iOS.
In essence, this means that if a user downloads the iOS 18.6 firmware and then tries to restore their device to it using the Shift key + Restore button in iTunes for Windows, or the Option key + Restore button in macOS, then it will no longer work as expected.
Firmware downgrades have long been used by users who wanted to jailbreak their iPhone or iPad, as older firmware typically has the greatest chance of being vulnerable to bugs and exploits. Apple got wise to this, and that’s why they unsign older firmware so frequently today.
It’s worth noting, however, that jailbreaking isn’t the only reason why firmware downgrades are important. Sometimes, when Apple releases a software update, unexpected bugs arise that can affect the performance or user experience of certain devices, such as in the various examples listed below:
- iPadOS 18.0 bricking M4 chip-equipped iPad Pros
- iOS 16.0 over-prompting users on clipboard access when pasting copied content into another app
- iOS 14.7 breaking the Apple Watch’s ability to be unlocked with the host iPhone’s Touch ID sensor
- iOS & iPadOS 13.2 imposing incredibly aggressive background management on backgrounded apps
When this happens, a firmware downgrade can act as a temporary remedy, allowing users to continue using their device until Apple can pull and re-issue the update, or release another software update that fixes the root problem.
Even though downgrades to iOS 18.6 from a newer firmware like iOS 18.6.1 or 18.6.2 is no longer possible, it’s worth noting that upgrades from an older firmware to iOS 18.6 should still be possible via the DelayOTA method, which takes advantage of an Enterprise-grade feature that allows upgrading to unsigned firmware within a 90-day grace period of being unsigned.
The iDB team has steadfastly supported the idea that iPhone and iPad users should be able to install any firmware they want on their device, regardless of the consequences. There should at least be an option for advanced users or Developer Account owners who wish to do this, despite Apple’s argument that they know best. Perhaps government regulation could force their hand at some point in the future.
As always, you can see what firmware is or isn’t being signed for your particular device by using the IPSW.me website. You can also download whatever firmware you might need for your device from our Downloads page.
