Jailbreaking is the process of removing manufacturer-imposed software restrictions on an iPhone to gain full access to the operating system. This allows you to install apps outside the official App Store and customize the device's interface and system files.
: Many banking, streaming, and high-security apps use "jailbreak detection" and will refuse to run on a modified device. Types of Jailbreaks How to Jailbreak iPhone
: Apple considers jailbreaking a "unauthorized modification" and may deny service for a jailbroken device. How to Jailbreak iPhone
: Requires running an app on the iPhone to re-enable the jailbreak every time the device restarts. How to Jailbreak iPhone