Nesbit

Spec sheet

Product

Nesbit is a toy NES emulator and debugger built from scratch in Swift for iOS, iPadOS, and macOS.Read 9 Oct 2026 · nesbit.app

Maker

The site identifies its maker as Jason and says he has over 13 years of experience writing software for Apple platforms.Read 4 Oct 2026 · nesbit.app

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.Read 9 Oct 2026 · nesbit.app

Audio

Nesbit plays sounds from all four synthesized channels.Read 9 Oct 2026 · nesbit.app

Beta availability

The linked TestFlight page says the beta is not accepting new testers.Read 4 Oct 2026 · testflight.apple.com

Controls

It provides an on-screen virtual controller on iOS and iPadOS and supports hardware keyboards and gamepads on all platforms.Read 9 Oct 2026 · nesbit.app

Debugger

Its debugger includes CPU status, disassembly, breakpoints, memory watches, a call stack, discovered subroutines, and step and run-to-instruction commands.Read 9 Oct 2026 · nesbit.app

Debugger ROM limit

The debugger supports ROMs using mapper 0.Read 9 Oct 2026 · nesbit.app

Downloads

The maker links to a TestFlight build for iOS and iPadOS and a macOS download.Read 9 Oct 2026 · nesbit.app

Game support

It supports NES games using mapper 0 or mapper 1.Read 9 Oct 2026 · nesbit.app

Limitations

Nesbit emulates one controller, does not play sampled audio, and does not implement some illegal CPU instructions.Read 4 Oct 2026 · nesbit.app

Open source

Nesbit is open source under the MIT License.Read 9 Oct 2026 · nesbit.app

Other limits

Nesbit emulates one controller, does not play sampled audio, and does not implement illegal CPU instructions that some software may use.Read 9 Oct 2026 · nesbit.app

Performance

The maker reports 60 FPS on M1 Macs and newer, and iPhone 14 Pro and newer.Read 9 Oct 2026 · nesbit.app

Playback

It plays sounds from all four synthesized channels and automatically restores each game's last state.Read 4 Oct 2026 · nesbit.app

Saved state

Nesbit automatically restores the state from the last time a given game was played.Read 9 Oct 2026 · nesbit.app

Source files

The debugger can load labels and subroutine names from .dbg files generated by the ca65 assembler.Read 4 Oct 2026 · nesbit.app

Where Specifiction places it

• NES Emulators#20 of 266.9