Codename One
Native apps in Java with a UI you control.
Codename One is an open-source framework that lets Java developers build native applications from a single codebase. It compiles one Java project into native binaries for mobile, desktop, web, watch, TV, and vehicle targets, with a custom-rendered UI packaged inside the app rather than restyled by the platform after release. The framework is licensed under GPLv2 with the Classpath Exception, so commercial use carries no royalties or per-app fees.
The framework provides a portable runtime, platform ports, and build tooling that works with Maven and common Java IDEs. Its simulator offers device skins, component and network inspectors, test recording, and live CSS editing. Developers can theme the shared UI with CSS, call platform SDKs through native interfaces, and embed heavyweight views such as maps, web views, or camera surfaces via PeerComponent. Cloud builds can produce app-store binaries, including iOS builds without a Mac. The tooling also supports agentic development through MCP integration with the simulator and JavaSE-hosted desktop tools, and exposes Java 17 project templates for coding agents.
Codename One is aimed at Java developers, from indie developers to enterprise teams, who want to maintain one application across multiple platforms. The framework itself is free for commercial use. A free cloud-build tier includes monthly build credits and a user JAR size limit, with JavaScript builds available on every tier. Paid plans are priced per developer seat and add higher build quotas, native platform sources, push notifications, Crash Protection, automated store submission, profile-guided optimization, and support.
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