Apple Stops Signing iOS 18.2.1, Preventing Downgrading

Apple today stopped signing iOS 18.2.1, which means that iPhone users who have upgraded to iOS 18.3 can no longer downgrade to the prior version of iOS 18. Apple released iOS 18.3 a week ago.

When new versions of iOS are released, Apple stops signing the prior version after a week or two. An update that is not signed is not able to be installed on an iPhone because there is a server-side software verification check. As of right now, iPhone models compatible with iOS 18 are only eligible to download and run iOS 18.3.

By preventing customers from downgrading to older versions of iOS, Apple ensures that devices are kept up to date with the newest security improvements.

Apple's iOS 18.3 update included a handful of Apple Intelligence updates and more than 20 security updates. One of those fixes addressed a vulnerability that may have been actively exploited on some devices, demonstrating why it is important to keep iOS software up to date.