Open Source Mobile Operating Systems Runtimes

Capacitor is an open source native runtime for building Web Native apps. Create cross-platform iOS, Android, and Progressive Web Apps with JavaScript, HTML, and CSS. Capacitor’s native plugin APIs make it extremely easy to access and invoke common device functionality across multiple platforms. Build web-based applications that run equally well across iOS, Android, and as Progressive Web Apps. Access the full Native SDKs on each platform, and easily deploy to the App Stores (and the web). Add custom native functionality with a simple Plugin API, or use existing Cordova plugins with our compatibility layer. Capture images, save photos, and configure hardware parameters like saturation and color balance. Save and read documents, assets, and other content your users need to access via native file systems. Gather critical information about a user’s device location, such as latitude and longitude.

J2ObjC is an open-source command-line tool from Google that translates Java source code to Objective-C for the iOS (iPhone/iPad) platform. This tool enables Java source to be part of an iOS application's build, as no editing of the generated files is necessary. The goal is to write an app's non-UI code (such as application logic and data models) in Java, which is then shared by web apps (using GWT), Android apps, and iOS apps. J2ObjC supports most Java language and runtime features required by client-side application developers, including exceptions, inner and anonymous classes, generic types, threads and reflection. JUnit test translation and execution is also supported. J2ObjC cannot convert Android binary applications. Developers must have source code for their Android app, which they either own or are licensed to use.

The Portable Object Compiler, a language and a runtime library for producing C programs that operate by the runtime conventions of Smalltalk 80 in a UNIX environment, as described in Brad Cox's book on Objective-C. The precompiler is backed by a library which supports Smalltalk 80's interpretatation of messaging; binding of a message to its target routine is done at run time.

injectionforxcode enables live code injection for iOS and macOS apps so developers can iterate on UI and logic without doing a full rebuild and relaunch. It works by compiling changed source files into dynamic bundles and loading them into the running app, swapping method implementations at runtime. The tool monitors file changes, triggers fast recompiles, and provides console feedback so you can confirm injections and quickly revert if needed. It supports Objective-C and Swift (with certain runtime caveats), and plays well with Interface Builder tweaks, letting you see visual changes almost immediately. Because it hooks into the natural development loop, it dramatically shortens feedback cycles for layout tuning, animations, and view controller logic. While not a replacement for clean rebuilds and full test runs, it’s a powerful productivity aid for day-to-day iteration.

The nativescript-ios repository contains the runtime and core modules necessary for building and running NativeScript applications on iOS devices, enabling developers to create native iOS apps using JavaScript or TypeScript.

nativescript-google-maps-sdk is a NativeScript plugin that integrates Google Maps into mobile applications. It offers a rich set of features for displaying maps, adding markers, and handling user interactions within NativeScript apps.

ios-jsc is a JavaScriptCore framework for iOS, utilized by NativeScript to execute JavaScript code within iOS applications. It provides a high-performance JavaScript engine that enables the execution of JavaScript in a native iOS environment.

iOS-Runtime-Headers is a large collection of Objective-C header files reconstructed from Apple’s private iOS frameworks and the public runtime. Its purpose is to expose class interfaces—methods, properties, ivars, protocols—that are not documented by Apple, making it easier to explore system behavior and reverse-engineer APIs. The headers are generated by inspecting binaries and metadata, then organized by framework so developers can browse relationships and inheritance hierarchies. This is invaluable for research, debugging, and tooling where you need to understand what UIKit, Foundation, or lower-level frameworks are actually doing under the hood. The project encourages read-only exploration; code using private APIs is generally unsuitable for App Store distribution. Practitioners use it to guide experiments, prototype ideas, and inform jailbreak or internal tooling where runtime knowledge is essential.