Despite the care that the Apple developer team puts in when they have to launch a new version of iOS, problems often arise after its installation on an iPhone or iPod, which are manifested in the form of untimely reboots, screen freezing, crashes in connectivity, among other errors.
How to fix update errors on an iPhone
Such errors are usually resolved after installing subsequent updates, but they can also be fixed by reverting to the immediately previous version of iOS.
However, this is not a procedure recommended by Apple, in addition, it has the disadvantage that a loss of information can occur due to an incompatibility between the backup files between different versions of iOS.
Another drawback is related to the digital signature of the firmware files available from old versions of IOS. Apple stops signing old copies of the iOS system periodically and fairly quickly, so that they are still available for download, iTunes will not allow the installation of an unapproved copy.
How to downgrade iOS on iPhone using iTunes
First of all, make a backup copy of the important information contained in your iPhone. Then open your preferred internet browser and go to the Apple Device Firmware File Download page: https://ipsw.me/.
Next, click on iPhone and select the model of your device. Download the firmware of the iOS version with which your device behaved in a stable way. Make sure it is signed by Apple.
After the above step is done, open iTunes and connect your iPhone to the computer using its data cable. Click on your device icon located at the top left of the iTunes window.
Holding down the Shift key, click Restore iPhone. If iTunes asks you to turn off Find My Iphone, do so. Then select the firmware file with the IPSW extension downloaded earlier.
Wait for the installation process of the previous version of iPhone to finish.
How to downgrade iOS on iPhone without iTunes
Download and install the 3uTools program on your PC. Open 3uTools and connect your iPhone to the computer. Click on the Smart Flash section.
Select the old version of iOS to which you plan to return and click Download, or click Import now if you already have the IPSW firmware file that corresponds to the model of your iPhone.
Then click Flash and wait for the downgrade process to finish to an older version of iOS.
Is it possible to downgrade from iOS 15 to iOS 14?
It is currently not possible to do this procedure, since the firmware file for iOS 14 is no longer signed by Apple.
See also:
How to find a stolen or lost iPhone