What is Cydia ?

Cydia is a software application for iOS that enables a user to find and install software packages (including apps, interface customizations, tweaks and system extensions) on a jailbroken iPhone, iPod Touch or iPad. Cydia is the main independent third-party digital distribution platform for software on iOS. Many of the software packages available through Cydia are free, and it also includes several hundred packages for sale through the Cydia Store payment system with a commission setup similar to the App Store. Most of these packages focus on providing customizations and modifications (often called "tweaks") that can only run on jailbroken devices (since the App Store is limited to distributing self-contained apps).


Cydia is a graphical front end to Advanced Packaging Tool (APT) and the dpkg package management system, which means that the packages available in Cydia are provided by a decentralized system of repositories (also called sources) that list these packages.
Cydia is developed by Jay Freeman (also called "saurik") and his company, SaurikIT. The name "Cydia" is an allusion to the Codling Moth, with a scientific name of Cydia pomonella, which is the proverbial "worm in the apple."

Purpose and function

Cydia provides a graphical user interface to jailbroken iOS users using APT repositories to install software unavailable on the App Store. Since Cydia is based on APT (ported to iOS as part of Freeman's Telesphoreo project), it is a repository aggregator that avoids dependence on one host and comes with a few trusted default sources. Many stable packages are available on these repositories, and additional repositories can be easily added. This enables the iOS development scene to stay as open as possible; anyone with a server can set up, host, manage, and update their own repository and share it with the community. The default sources accept package submissions, which helps packages gain more exposure than if they were hosted on separate repositories.

Software packages are downloaded directly to an iOS device, to the same location as Apple's pre-installed applications, the /Applications directory. Jailbroken devices can also still buy and download apps normally from the official App Store.

Some of the packages available through Cydia are standard applications, but most of the packages are extensions and modifications for the iOS interface and for apps in the iOS ecosystem. Since these software packages run on jailbroken devices, they can provide functionality outside the scope of normal applications — such as system-wide changes to the user interface, new features inserted into existing apps, customizations of button actions, extensions of networking behavior, and other "tweaks" to the system. Users install these for purposes including personalization and customization of the interface, adding desired features and fixing annoyances, and making development work on the device easier by providing access to the filesystem and command-line tools. Most of the packages available through Cydia are written by independent developers

Cydia is installed during the process of jailbreaking an iOS device. Jailbreaking tools (each of them supporting a specific set of devices and iOS versions) including ZiPhone, JailbreakMe, QuickPwn, redsn0w, purplera1n, blackra1n, limera1n, Greenpois0n, and Absinthe include the option to install Cydia while jailbreaking or install Cydia automatically while jailbreaking, and Cydia can also be installed by restoring a custom jailbroken firmware created by the jailbreaking tools PwnageTool, sn0wbreeze or redsn0w.