# flutter > Google's free, open source, and cross-platform mobile app SDK. > Some subcommands such as `flutter pub` have their own usage documentation. > More information: . - Initialize a new Flutter project in a directory of the same name: `flutter create {{project_name}}` - Check if all external tools are correctly installed: `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}}` - Build a release APK targeting most modern smartphones: `flutter build apk --target-platform {{android-arm}},{{android-arm64}}` - Display help about a specific command: `flutter help {{command}}`