# flutter > Google's free, open source, and cross-platform mobile app SDK. > More information: . - Check the Flutter version: `flutter --version` - Display general help: `flutter help` - Display help about a specific command: `flutter help {{command}}` - Execute a Flutter command: `flutter {{command}}` - Show information about the installed tooling: `flutter doctor` - List or change Flutter channel: `flutter channel {{stable|beta|dev|master}}` - Run Flutter on all started emulators and connected devices: `flutter run -d all` - Run tests in a terminal from the root of the project: `flutter test {{test/example_test.dart}}`