An IPSW file is a proprietary archive format used by Apple to distribute firmware updates for iOS, iPadOS, tvOS, and watchOS devices. It contains all the necessary files to restore or update an Apple device's operating system. These files include the bootloader, baseband firmware, system software, and other device-specific components. The IPSW file is essentially a complete image of the device's software, allowing users to perform a clean install or restore to a previous version. Users typically download IPSW files from Apple's servers or third-party websites. Restoring or updating via IPSW is often used to bypass over-the-air updates, downgrade to older iOS versions (when Apple allows), or recover a device that is stuck in a boot loop. The process involves using iTunes or Finder (on macOS Catalina and later) to select the IPSW file and initiate the restore or update process. It's crucial to download IPSW files from trusted sources to avoid installing malicious software. The integrity of the IPSW file is usually verified by the software before installation.