Gameboy emulator implemented in C
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Travis AppVeyor


A simple GB/GBC emulator.


  • Runs in the browser using WebAssembly
  • Hacky-but-passable CGB support!
  • Cycle accurate, passes many timing tests (see below)
  • Supports MBC1, MBC1M, MMM01, MBC2, MBC3, MBC5 and HuC1
  • Save/load battery backup
  • Save/load emulator state to file
  • Fast-forward, pause and step one frame
  • Rewind and seek to specific cycle
  • Disable/enable each audio channel
  • Disable/enable BG, Window and Sprite layers
  • Convenient Python test harness using hashes to validate
  • (WIP) Debugger with various visualizations (see below)

DMG Screenshots

Bionic Commando Donkey Kong Kirby's Dreamland 2 Mole Mania Mario's Picross Trip World Wario Land Game Boy Wars Is That a Demo in Your Pocket?

CGB Screenshots

Dragon Warrior Hamtaro Metal Gear Solid It Came From Planet Zilog Survival Kids Aevilia Toki Tori Wario 3

Debugger Screenshots

Debugger OBJ Map Tile Data Breakpoints


Requires CMake and SDL2. Debugger uses dear imgui, (included as a git submodule).

Building (Linux/Mac)

If you run make, it will run CMake for you and put the output in the bin/ directory.

$ make
$ bin/binjgb

You can also just use cmake directly:

$ mkdir build
$ cd build
$ cmake ..
$ make

Building (Windows)

When building on Windows, you'll probably have to set the SDL2 directory:

> mkdir build
> cd build
> cmake .. -G "Visual Studio 14 2015" -DSDL2_ROOT_DIR="C:\path\to\SDL\"

Then load this solution into Visual Studio and build it. Make sure to build the INSTALL target, so the exectuables are built to the bin directory.

Building WebAssembly

You can build binjgb as a WebAssembly module. You'll need an incoming build of emscripten. See and

Put a symlink to Emscripten in the emscripten directory, then run make.

$ ln -s ${PATH_TO_EMSCRIPTEN} emscripten
$ make wasm

Changing the Build Configuration

If you change the build config (e.g. update the submodules), you may need to run CMake again. The simplest way to do this is to remove the out/ directory.

$ rm -rf out/
$ make


$ bin/binjgb <filename>
$ bin/binjgb-debugger <filename>


Action Key
Quit Esc
Save state F6
Load state F9
Toggle fullscreen F11
Disable audio channel 1-4 1-4
Disable BG layer B
Disable Window layer W
Disable OBJ (sprites) O
Fast-forward Lshift
Rewind Backspace
Pause Space
Step one frame N

Running tests

Run scripts/ to download and build the necessary testsuites. This works on Linux and Mac, not sure about Windows.

scripts/ will only run the tests that match a filter passed on the command line. Some examples:

# Run all tests
$ scripts/

# Run all tests mooneye tests
$ scripts/ mooneye

# Run all gpu tests
$ scripts/ gpu

Test status

See test results