Once those updates dry up, it’s rare for Apple to revisit those older operating systems, but the company does sometimes make exceptions. Both iOS 15 and iOS 16 were last patched in mid-2025, but iOS 12’s last patch was released in January of 2023. Oddly, the iOS 16 update doesn’t mention the security certificate, and there’s no equivalent update for devices stuck on iOS 17. Devices running old iOS versions like iOS 12, 15, and 16 are difficult if not impossible to use as general-purpose smartphones and tablets these days. Third-party apps also mostly stop supporting old iOS versions after a year or two.