Apple recently stopped the ability to downgrade to iOS 18.2.1.
The Cupertino-based company regularly rolls out updates to its new devices, and after a while, it stops signing older software versions. This has happened to iOS 18.2.1, which means that iPhone users with the device version 18.3 will no longer be able to downgrade. As updates are done using a server verification check, the device will show an error that this is no longer possible. As it stands, all iPhone models that can run iOS 18 are forced to stay in iOS 18.3.
iOS 18.3 introduces several new features and updates, including security fixes and Apple Intelligence. It’s believed that one of the fixes was to prevent an exploit from being accessed. Apple claims that keeping up to date ensures a high level of security for users, hence the stop-signing of older iOS versions.
