Within a week of iOS 18.3 launching, Apple has ceased signing iOS 18.2.1. As a result, once you perform an update on your iPhone or iPad to 18.3, there will be no going back to 18.2.1.
For context, iOS 18.2.1 had been released on January 6 to address some “important bug fixes,” with no clarification by Apple on the specifics. iOS 18.3 was released on January 27, and it included a number of exciting improvements, particularly a blessedly friendly enhancement in Apple Intelligence features, as well as several security patches. One of the key features in this update debugs an AirPlay security flaw which might allow attackers to access your device via the local network, and that’s not the experience you’d probably love!
It is usually good to ensure devices are updated, as newer versions can only bring newer features and the latest security provisions. If you should experience any hitches after the iOS 18.3 update, remember that restoring iOS 18.2.1 if you wish will not be an option. Apple typically stops signing older iOS versions to protect its users from known vulnerabilities that have already been patched. So feeling restricted may be somewhat devious, but the basic demand is to protect your device and personal information!