Plug your iPhone into a computer, open Finder/iTunes, and click on the serial number. It will rotate to show UDID, then ECID.
./futurerestore -t blob.shsh2 -s signed_sep.im4p -b baseband.bbfw iPhone.ipsw ecid register iphone exclusive
Understanding how to register your iPhone’s ECID, what it does, and why it is "exclusive" is crucial for jailbreaking, upgrading, downgrading, or managing your device at a low-level. What is an ECID (Exclusive Chip ID)? Plug your iPhone into a computer, open Finder/iTunes,
While ECID registration offers numerous benefits, there are challenges and limitations to consider: Plug your iPhone into a computer
Contains numbers and letters (A–F). Example: 0011A2B3C4D5E6F7