Using tools like iTunes (Windows/older macOS) or Finder (modern macOS), you can install the custom firmware. You will often need to put your device into DFU mode for the installation to be accepted. Alternatives to Modifying IPSW Files
You will need AES decryption keys to decrypt older iOS firmware. Websites like the iPhone Wiki archive these keys. Step-by-Step: How to Modify an IPSW File Step 1: Download the Target IPSW
For security auditing or older device recycling, developers sometimes modify ramdisks to skip specific setup screens. modify ipsw file
While modifying an IPSW on your computer is relatively straightforward, Apple protects its devices using hardware-rooted security features that make custom IPSWs nearly impossible to flash on modern devices: 1. SHSH2 Blobs and APTicket Verification
Apple uses a Cryptographic Verification System called . When iOS boots, the SEP and iBoot bootloader check a digital signature inside the IPSW against Apple's signing server. If the signature is missing or invalid—even by one bit—the device refuses to boot. Modern devices (A12+ chips) have a hardware fuse called the Nonce . This means you cannot simply flash a modified IPSW; you need a bootrom exploit (rare) or a jailbreak that bypasses signature checks after boot. Using tools like iTunes (Windows/older macOS) or Finder
The legal landscape surrounding IPSW modification is nuanced. For personal, non-commercial use on devices you own, modifying firmware generally falls into a legal gray area. However, distributing modified IPSW files or using them to circumvent paid services like iCloud activation lock may violate terms of service and, in some jurisdictions, applicable laws.
imgsync sign <IPSW file> <Apple ID> <password> Websites like the iPhone Wiki archive these keys
idevicerestore -e custom_firmware.ipsw