Nesbit
Nesbit is a free, open-source NES emulator and debugger written from scratch in Swift for iOS, iPadOS and macOS.
What Nesbit is
Nesbit is a free, open-source NES emulator and debugger written from scratch in Swift for iOS, iPadOS and macOS. It supports games using mapper 0 or 1, while debugging is limited to mapper 0. Players can use an on-screen controller on iOS and iPadOS, with hardware keyboards and gamepads supported across all listed platforms. Nesbit plays audio from all four synthesized channels and restores each game's previous state automatically. Its debugger shows CPU status and disassembly, with views for breakpoints, memory watches, call stacks and subroutines. It can load labels and subroutine names from ca65-generated .dbg files; macOS reloads them with ROMs, while iPhone and iPad require manual loading each time. The site reports 60 FPS on M1 Macs and newer and iPhone 14 Pro and newer. The project uses the MIT License. Downloads include a macOS build and TestFlight links, though the linked beta is not accepting new testers.
Good
- Free and MIT-licensed open source
- Supports NES mapper 0 and 1 games
- Includes CPU and disassembly debugger views
- Restores each game's last state
- Supports keyboards and gamepads
Watch out
- Debugger supports mapper 0 ROMs only
- Emulates one controller
- Does not play sampled audio
- TestFlight beta is not accepting new testers
Who it suits
Nesbit suits Apple-platform users who want NES playback or development-oriented debugging. It is also relevant to readers seeking an open-source Swift project.
Verdict
Nesbit combines NES emulation with a focused debugger on Apple platforms. Its mapper, controller, audio and beta limitations matter when choosing it for specific games or testing.
The facts
Each one read from Nesbit's own pages, with the date it was checked.
What it does
- Assembler labels
- The debugger can load labels and subroutine names from ca65-generated .dbg files; files are automatically reloaded with ROMs on macOS, while iPhone and iPad require manual loading each time.checked 9 Oct 2026
- Audio
- Nesbit plays sounds from all four synthesized channels.checked 9 Oct 2026
- Beta availability
- The linked TestFlight page says the beta is not accepting new testers.checked 4 Oct 2026
- Controls
- It provides an on-screen virtual controller on iOS and iPadOS and supports hardware keyboards and gamepads on all platforms.checked 9 Oct 2026
- Debugger
- Its debugger includes CPU status, disassembly, breakpoints, memory watches, a call stack, discovered subroutines, and step and run-to-instruction commands.checked 9 Oct 2026
- Debugger ROM limit
- The debugger supports ROMs using mapper 0.checked 9 Oct 2026
- Downloads
- The maker links to a TestFlight build for iOS and iPadOS and a macOS download.checked 9 Oct 2026
- Game support
- It supports NES games using mapper 0 or mapper 1.checked 9 Oct 2026
- Limitations
- Nesbit emulates one controller, does not play sampled audio, and does not implement some illegal CPU instructions.checked 4 Oct 2026
- Open source
- Nesbit is open source under the MIT License.checked 9 Oct 2026
- Other limits
- Nesbit emulates one controller, does not play sampled audio, and does not implement illegal CPU instructions that some software may use.checked 9 Oct 2026
- Performance
- The maker reports 60 FPS on M1 Macs and newer, and iPhone 14 Pro and newer.checked 9 Oct 2026
- Playback
- It plays sounds from all four synthesized channels and automatically restores each game's last state.checked 4 Oct 2026
- Product
- Nesbit is a toy NES emulator and debugger built from scratch in Swift for iOS, iPadOS, and macOS.checked 9 Oct 2026
- Saved state
- Nesbit automatically restores the state from the last time a given game was played.checked 9 Oct 2026
- Source files
- The debugger can load labels and subroutine names from .dbg files generated by the ca65 assembler.checked 4 Oct 2026
The company
- Maker
- The site identifies its maker as Jason and says he has over 13 years of experience writing software for Apple platforms.checked 4 Oct 2026