Apple last week released iOS 12.5.1 for older devices, and as is traditional, Apple has now stopped signing iOS 12.5, making downgrading to that version of iOS no longer possible.
Apple in December released an iOS 12.5 update, which enabled the use of the Exposure Notifications system to older devices. The iOS 12.5.1 update addresses a bug that could cause Exposure Notifications to incorrectly display logging profile language.
Apple’s Exposure Notifications system is now available in multiple U.S. states, as well as numerous countries. States adopting the system include North Dakota, Arizona, Delaware, Nevada, Alabama, Colorado, Wyoming, North Carolina, Pennsylvania, Michigan, Maryland, New York, New Jersey, Minnesota, Washington, Connecticut, Nevada, the District of Columbia, and California.
Apple is known to routinely stop signing older versions of operating systems after it releases a public update, as part of an effort to encourage users to keep their devices’ operating systems up to date.
As noted by 9to5Mac, reverting to older iOS builds is a common activity for those with jailbroken devices. Also, restoring an iPhone or iPad to a previous version of iOS can be helpful for users who experience significant bugs after upgrading to the latest version of iOS.