It uses previously saved SHSH blobs (digital signatures from when the iOS version was still signed) to trick your device into accepting the older firmware.
The Ultimate Guide to Unsigned IPSW Restore Tools: Can You Downgrade iOS for Free? unsigned ipsw restore tool free
A cross-platform command-line tool part of the libimobiledevice project. It's essentially an open-source implementation of the iTunes restore process. It uses previously saved SHSH blobs (digital signatures
Your device will enter Recovery Mode. FutureRestore will bypass Apple's verification servers using your blob and flash the unsigned firmware to your device. Do not unplug the cable until the terminal says the process is complete. Beware of Scams: "No-Blob" Paid Tools It's essentially an open-source implementation of the iTunes
(like iMyFone Fixppo or ReiBoot) do not actually restore unsigned firmware. They fix recovery loops or downgrade only while the window is still open . Always read the fine print.
: These are unique to your specific device. You cannot use someone else's blobs to restore your phone. 🔍 How to Check Signing Status
An unsigned IPSW file is a firmware image that is no longer being signed by Apple. When Apple releases a new iOS version, it stops signing older versions, making it difficult for users to restore their devices to those versions.