Apple has stopped signing iOS 15.4 just over a week after releasing iOS 15.4.1 to the public. This means it is no longer possible to downgrade your iPhone to the older version of the operating system. The company also stopped signing iPadOS 15.4, so you cannot downgrade your iPad to the older firmware either.
Apple stops signing iOS 15.4
It is typical for Apple to stop signing older versions of iOS and iPadOS once it releases a new build. Usually, iPhone users only look to downgrade their device to an older firmware if they encounter a significant bug in the latest release or if they plan to jailbreak it. In the latter situation, you should always stay on the oldest iOS firmware possible, as the chances of a jailbreak tool coming out for it are higher.
This move from Apple won’t affect your iPhone in any way if it is running iOS 15.4 — you can always upgrade to the latest available firmware without any issues.
iOS 15.4.1 fixes a battery drain bug on iPhones
Apple dropped iOS 15.4.1 at the very end of March with some bug fixes and security updates, including a fix for the excessive battery drain on iPhones running iOS 15.4. The official release notes for the update are as follows:
iOS 15.4.1 includes bug fixes and security updates for your iPhone and is recommended for all users.
This update includes the following bug fixes for your iPhone:
Battery may drain more quickly than expected after updating to iOS 15.4
Braille devices may become unresponsive while navigating text or displaying an alert
Made for iPhone hearing devices may lose connection within some third-party apps
The company also released watchOS 8.5.1, tvOS 15.4.1, and macOS 12.3.1 on the same day with minor bug fixes.
If you have not already, you should install the iOS 15.4.1 update on your iPhone, especially since it fixes the battery drain issue.