NEShim Documentation

NEShim is a full-featured NES emulator built on BizHawk’s cycle-accurate core, with native Steam integration for commercial distribution. Publish any NES game on Steam as a native Windows or Linux application — with achievements, overlay support, Steam Input, save states, a rich multi-language UI, and a deep video and audio filter stack — without modifying the ROM.

Documentation

Page What it covers
Configuration reference Every field in config.json, with types, defaults, and examples
Filters Audio filters (7 processors), video filters (structural, overlay, color effects, motion effects), availability by renderer, combining examples, and shader architecture
Achievement system How to define memory-watch triggers, encode them, and seal the config
Publishing guide Step-by-step checklist for packaging a game for Steam release
Multi-Game Mode An alternate, additive publish path: one binary hosting N games, each bundled in a single deploy or sold as separate Steam DLC, selected through a front-end filmstrip carousel with per-game box art and descriptions
Architecture Internals: thread model, subsystem design, patterns, how to extend
Input system Keyboard remapping, XInput, Steam Input, hotkeys, and the VDF file
Localization Language files, Steam language detection, CJK font fallback
Steam Deck Automatic adjustments (menu scale, audio default), input latency fix, publishing requirements, known differences from Windows

Requirements

  • Windows x64: Windows 10 or later; D3D11 rendering path (SDL_GPU/Vulkan fallback if D3D11 unavailable)
  • Linux x64: SDL_GPU/Vulkan rendering path; runs natively on Ubuntu 22.04+, SteamOS, and other mainstream distros
  • .NET 9 runtime (bundled in self-contained publish)
  • Steam client — required for achievements and overlay; the emulator runs without it but Steam features are silently disabled
  • Steamworks native library — must be placed alongside the executable; not included in the repository (Valve SDK license). Use the matching copy from the Steamworks.NET 2025.163.0 release zip: steam_api64.dll (Windows) or libsteam_api.so (Linux) renamed to libsteam_api64.so — the wrapper’s native-library lookup resolves to that name; under the zip’s default Linux filename, Steam init fails at startup (caught internally — the app still runs, but achievements/overlay/DLC checks are silently disabled). Games deployed through Steam receive it automatically via the Steam depot.
  • A .nes ROM file

Quick start (publishers)

Place config.json alongside the executable and set romPath at minimum:

{
  "romPath": "mygame.nes",
  "windowTitle": "My Game"
}

Everything else has sensible defaults. See the configuration reference for the full list.

Quick start (developers / contributors) 

# Build the full solution
dotnet build NEShim/NEShim.sln

# Run tests
dotnet test NEShim/NEShim.Tests/NEShim.Tests.csproj

# Publish the game — Windows (self-contained, win-x64, with ReadyToRun)
dotnet publish NEShim/NEShim/NEShim.csproj -c Release -r win-x64 --self-contained true -p:PublishReadyToRun=true -o publish/NEShim-win-x64

# Publish the game — Linux (cross-compiles from Windows, or run on Linux)
dotnet publish NEShim/NEShim/NEShim.csproj -c Release -r linux-x64 --self-contained true -p:PublishReadyToRun=true -o publish/NEShim-linux-x64

# Or publish all platforms at once using the publish script:
.\local-publish.ps1 1.0.0

After publishing, copy the Steamworks native library from the Steamworks.NET GitHub release zip into the output directory alongside the exe: steam_api64.dll for Windows, libsteam_api.so for Linux — rename the Linux file to libsteam_api64.so (the wrapper’s native-library lookup resolves to that name; Steam init fails at startup under the zip’s default name, caught internally and silently disabling achievements/overlay/DLC checks). See the publishing guide for details.

See the architecture guide for a detailed walkthrough of the codebase.