JUCE is an open source, cross-platform, software development framework provided as C++ source code, that can be used to create standalone software on Windows, macOS, Linux, iOS and Android, as well as VST, VST3, AU, AUv3, AAX and LV2 plug-ins.
You can find the JUCE source code in a public repository on GitHub.
JUCE can be easily integrated into your existing projects, with support for CMake alongside direct generation of Xcode projects, Visual Studio solutions, Android Studio projects, and Makefiles.
The JUCE Framework is the most widely used framework for audio application and plug-in development, and is used by all of the most important companies that deal with audio, either supporting their in-house research and development software, or in their publicly released products.
JUCE allows developers to focus on the most valuable parts of their software by taking care of the differences between operating systems (both desktop and mobile) and plug-in formats. With your project based on the JUCE framework you can write software once and have it work the same way wherever you deploy.