iOS & i4Tools Glossary

Definitions of common terms you’ll see when using i4Tools, iTunes, or managing your iPhone, iPad, or iPod touch.

A–C

Activation Lock: An Apple security feature that ties a device to the Apple ID used with “Find My.” The device cannot be used until that Apple ID is entered. See iCloud Bypass (for supported cases only).
Backup: A copy of your device’s data (settings, apps, photos, etc.) stored on a computer or in iCloud. i4Tools can create and manage backups. See Backup & Restore.
DFU (Device Firmware Update) Mode: A low-level mode where the device does not load the full iOS. Screen stays black. Used for restore, downgrade (when signed), or jailbreak. See DFU and Recovery Mode.
ECID: Exclusive Chip Identifier. A unique number for your device’s chip, used in restore and some advanced operations. i4Tools can display it. See Device Information.

Firmware: The device’s operating system (e.g. iOS 17, iPadOS 18). “Flashing” firmware means installing or reinstalling it. See Firmware Flashing.
Flashing: Installing or reinstalling iOS/iPadOS on the device, often via restore. i4Tools supports one-click flashing. See Firmware Flashing.
IMEI: International Mobile Equipment Identity. A unique number that identifies your phone on cellular networks. i4Tools can show it. See Device Information.
IPSW: iPhone/iPad Software (update file). The file that contains the iOS image used for restore or update. i4Tools can download and use IPSW files.
iTunes: Apple’s official desktop app (Windows) for backup, restore, and sync. On newer Macs, many of these functions are in Finder. See i4Tools vs iTunes.

Jailbreak: Removing Apple’s software restrictions so you can install unauthorized apps and tweaks. i4Tools can work with certain jailbreak tools. See Jailbreak.
Recovery Mode: A mode that shows “connect to iTunes” (or cable) on the screen. Used to restore the device when it’s stuck or failed. See DFU and Recovery Mode.
Restore: Reinstalling iOS on the device (and usually erasing all data), or restoring data from a backup. i4Tools and iTunes both can restore. See Backup & Restore and Firmware Flashing.

Serial Number: A unique identifier for your device. Used for warranty and support. i4Tools can display it. See Device Information.
Signing (Apple): Apple “signs” iOS versions for a limited time. You can only install or restore to a version that is currently signed. Downgrades are only possible when the older version is still signed.
UDID: Unique Device Identifier. A string that uniquely identifies your device to developers and some services. i4Tools can show it.