Apple Stops Signing iOS 15.3.1 Following iOS 15.4 Release, Downgrading No Longer Possible
Following the release of iOS 15.4 on March 14, Apple has stopped signing iOS 15.3.1, the previously available version of iOS that came out in February. As iOS 15.3.1 is no longer being signed, it is not possible to downgrade to that version of iOS if you've updated to iOS 15.4.

Apple routinely stops signing older versions of software updates after new releases come out in order to encourage customers to keep their operating systems up to date, so it is not unusual that iOS 15.3.1 is no longer being signed.
iOS 15.3.1 was a bug fix update that addressed WebKit vulnerabilities, while iOS 15.4 was a major update that added new emoji characters, Face ID with a mask support, and tons of other features. Apple has also stopped signing tvOS 15.3.
Popular Stories
Apple is set to unveil new iPhone 18 Pro and iPhone 18 Pro Max models on Wednesday, September 9, and the devices are expected to feature a design that's largely similar to the iPhone 17 Pro models, with a peppering of enhancements inside. Major changes are not expected until next year, when Apple is expected to introduce a radically redesigned 20th-anniversary iPhone.
If you're thinking of...
While the iPhone 17 Pro has double the base storage compared to the iPhone 16 Pro, there will apparently be no further increase this year.
Taiwanese research firm TrendForce today again reported that the iPhone 18 Pro models will start with 256GB of storage, like the iPhone 17 Pro models.
Minimum storage capacities by model:iPhone 16 Pro: 128GB
iPhone 17 Pro: 256GB
iPhone 18 Pro...
Apple's first foldable iPhone, dubbed the "iPhone Ultra," is expected to launch without at least four features that will be present on the iPhone 18 Pro models, despite a price tag of at least $2,000.
The iPhone Air lacks Ultra Wide and Telephoto rear cameras, a SIM card slot, and stereo speakers. With a super thin design, a titanium frame, and a glass back, the iPhone Ultra is expected to ...