This article is for educational purposes and for those working with older, legacy devices (specifically, those powered by 32-bit processors, mostly iPhones 4s and earlier). Here's everything you need to know about what IPSWs are, why and how to modify them, and why Apple has made it so difficult.
For newer devices with format, you need img4tool :
: Historical tools used for legacy devices to create custom IPSWs. modify ipsw file
The Ultimate Guide to Modifying IPSW Files: Custom iOS Firmware Explained
Since the IPSW format is based on ZIP compression, you can access the internal files easily: Rename the file extension from Right-click and select Extract All or use a tool like What's inside: You will see multiple (Disk Image) files, a BuildManifest.plist , and various firmware folders. 2. Modify the File System (Advanced) The largest file typically contains the Root File System Mount the DMG This article is for educational purposes and for
Modern Apple devices (A12+ chips) use strictly enforced digital signatures. Modifying an IPSW will break its cryptographic signature, making it impossible to install on standard devices unless you use specific hardware exploits (like checkm8 for older devices). 1. Extracting the IPSW Contents An IPSW file is essentially a renamed ZIP archive .
Double-click the DMG to mount it. If it is read-only, use Disk Utility to convert it to a "Read/Write" image first. The Ultimate Guide to Modifying IPSW Files: Custom
: If you have a device from this era, do not expect to build and flash a custom IPSW.
vfdecrypt -i encrypted_rootfs.dmg -k [AES_KEY] -o decrypted_rootfs.dmg Use code with caution. Step 4: Mount and Modify the Contents Once decrypted, you can mount the DMG file.
Connect your iOS device to your computer and use iTunes to install the modified IPSW file.