Apple today stopped signing iOS 26.2, which means that iPhone users who have updated to iOS 26.2.1 are no longer able to downgrade to the earlier version of iOS. Apple released iOS 26.2.1 last week with support for the AirTags 2.

Software "signing" means that it has passed the server-side verification check that Apple performs when a user downloads a new version of iOS on an ‌iPhone‌. An update can't be installed unless it passes the verification check.

Apple does not show users earlier versions of iOS once an upgrade has come out, but when software is still signed, it is possible to downgrade using the macOS Finder on a Mac or the Apple Devices app on a Windows PC. Until today, users would have been able to downgrade from iOS 26.2.1 to iOS 26.2 if desired for some reason.

Unsigning software prevents Apple customers from installing outdated, less secure versions of iOS, and Apple typically stops signing an update a week or so after new software comes out.

Apple has also stopped signing several older versions of iOS provided for devices unable to update to iOS 26, including iOS 12.5.7, iOS 15.8.5, iOS 16.7.12, and iOS 18.7.3. iOS 12.5.8, iOS 15.8.6, and iOS 18.7.4 were released last week, while an updated version of iOS 16 came out today.

Source: Macrumors