Flutter is a new way to build high-performance, cross-platform mobile apps. Flutter is optimized for today's, and tomorrow's, mobile devices. We are focused on low-latency input and high frame rates on Android and iOS. The Flutter Engine is a portable runtime for hosting Flutter applications. It implements Flutter's core libraries, including animation and graphics, file and network I/O, accessibility support, plugin architecture, and a Dart runtime and compile toolchain. Most developers will interact with Flutter via the Flutter Framework, which provides a modern, reactive framework, and a rich set of platform, layout and foundation widgets.