Granny Smith is a browser-first 68000 Macintosh emulator.
Try Granny Smith instantly in your browser!
For best results, use a Chromium-based browser (Chrome, Edge, etc.). Safari has known issues.
The guiding principle for this project is to "keep it simple" — simple for everyone to run classic Macintosh software as well as simple to develop and maintain the emulator itself.
- Run in the browser – no installation needed
- Continuous background checkpointing – reload or close the browser without losing your running session
- Mount disk images by drag-and-drop – even if they're compressed in
*.sit.hqxformat - Access the browser/host filesystem through a built-in AFP file server
- Extensive automated testing – unit tests, headless integration tests, and Playwright end-to-end tests
- Highly portable C99 core – no special runtime requirements
- Simple CPU model – no advanced JIT compiler or meta tools; we rely on the compiler and modern hardware to make it fast enough
- Compact and maintainable – the entire CPU instruction decoder is under 550 lines and all opcode implementations fit in under 1,000 lines (new 68030/40 support excluded)
- Comprehensive documentation – hardware documentation in Markdown format, easily accessible for both human developers and AI agents
- AI agent friendly – repository organized to simplify work for coding agents
To run Granny Smith you need a Macintosh Plus ROM image and a bootable system disk image. Both are loaded by drag-and-drop in the browser — no other configuration required.
- Open Granny Smith in any modern browser
- Drag a Macintosh Plus ROM file onto the emulator window
- Drag a bootable disk image (e.g., a System 6
.dskfile) onto the window - The emulator boots automatically — your session is saved continuously in the background
Disk images can be raw (.dsk, .img) or compressed (.sit.hqx). The emulator decompresses them on the fly via the bundled peeler library.
If you want to build and run Granny Smith locally (e.g., for development or to enable audio via SharedArrayBuffer):
make run # Build and start HTTP server on :8080This builds the WebAssembly version and starts a local server with the required COOP/COEP headers for advanced features like audio. See CONTRIBUTING.md for detailed build instructions.
- All relevant Macintosh Plus hardware fully emulated (no ROM patching)
- Accurate enough timing (MacTest hardware test suite runs without errors)
- Mounting of compressed disk images (e.g.,
*.sit.hqx) via the peeler library - Background checkpointing and on-demand checkpointing/restore
- Browser filesystem accessible as an AFP share with authentication and file browsing
- LaserWriter emulation incomplete – printer is identified but print jobs don't finish correctly
- AFP file content access not yet implemented (just mounting/browsing)
The easiest way to get up and running is by creating a GitHub Codespace based on the repository. From the granny-smith code page, click Code (the big green button) → Codespaces → Create a Codespace on main. It will take a minute or two, then you're up and running.
make # Build the WASM emulator
make run # Build and start the HTTP server on :8080To pre-load boot media, pass paths (relative to the repo root) as make variables:
make run ROM=path/to/rom.bin HD0=path/to/hd.zipAvailable options for the run target:
| Variable | Description |
|---|---|
ROM=path/to/rom.bin |
ROM image |
FD0=path/to/floppy.img |
Floppy disk image |
HD0=path/to/hd.zip … HD7=… |
Hard disk images (zip or raw) |
SPEED=max|realtime|hardware |
Emulation speed |
Example:
make run ROM=tests/data/roms/Plus_v3.rom HD0=tests/data/systems/hd.zipBuild and test instructions: See CONTRIBUTING.md
Architecture and design docs: See docs/ARCHITECTURE.md
Coding guidelines: See AGENTS.md
| Area | Directory |
|---|---|
| Browser frontend | app/web/ |
| CPU core | src/core/cpu/ |
| Peripherals | src/core/peripherals/ |
| Machine definitions | src/machines/ |
| Hardware documentation | docs/ |
- Finalize LaserWriter emulation and AFP file server
- Add support for OPFS (to replace idbfs) for persistent browser storage
- Add an Electron build target (just placeholder today)
- Add support for 68030-based Macintosh models
- Bootstrap A/UX
- raddad772 for the 68K test suite (single-step-tests)
- xterm.js for terminal emulation in the browser
- JSZip for ZIP file handling
- Emscripten for the WebAssembly toolchain
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