ClassicBoy series apps are powerful emulator front-ends coming with multiple emulator cores (also called  as 'plugins' in app) that simulate dozens of retro video game consoles. Most cores have been merged into the app but some of them need to be downloaded and installed manually due to their big sizes or special licenses. Unlike other emulators front-end, ClassicBoy uses a special architecture that puts user events in native buffer and provides a general interface for all cores to work with. By this means, After the game starts, ClassicBoy works in 'passive' mode, the core decodes ROM data and polls user events to generate video and audio data and then requests the native engine to render, because the entire process is completed in native layer, higher performance and smoother video and audio effects can be achieved.

ClassicBoy leads gestures mapping into game controller, it’s very useful for game controlling on smartphone or tablet with touchscreen. When switches to gestures controller, left side on screen for directions and right side for actions mapping, there are 8 swipe directions can be detected on each side of screen and each one can be mapped to a game button. Besides gestures controller, accelerometer sensor (depends on hardware) is supported to simulate D-pad and calibration console is also provided for fine adjustment of tilt parameters. 

The gestures/sensor controller and state resume functions are only supported in premium version, but traditional input means such as on-screen buttons and gamepad mapping are supported as base functions in the free version. All these game controllers can be switched at runtime. For on-screen buttons, a powerful layout editor can be used to define the position and size for each button. Maximum 4 players can be added to map to external gamepad.

ClassicBoy series includes 2 apps: ClassicBoy Lite and ClassicBoy Pro. The Lite version with green theme focuses on  emulating the classic retro games that are well known in the world, it has a lightweight UI theme to launch core menu and import/export games. The Pro version with purple theme focuses on user convenience by supporting games search and identification, it also extended to emulate more games by supporting external plugins installation.