JSNES vs Nestalgia

JSNES is a free JavaScript library for emulating NES games in browsers and Node.js. Its Browser helper handles canvas rendering, audio, keyboard and gamepad input, and frame timing; the lower-level NES class allows custom rendering and audio handling in Node.js. ROM data can be loaded from a URL or from a string, Uint8Array, or ArrayBuffer. The API runs frames, accepts controller input for either player, resets, adjusts frame rate, and includes methods for moving and triggering the Zapper. Applications can serialize and restore emulator state with `toJSON()` and `fromJSON()`. The `onBatteryRamWrite` callback lets an application capture battery-backed SRAM writes for persistent game saves. Sound emulation is enabled by default, with a default sample rate of 48000 Hz, and an audio callback is available. The README provides npm installation for Node.js or Webpack and an unpkg script for browser use, as well as a React embedding example. JSNES is licensed under Apache-2.0; its GitHub Issues tracker accepts bug reports and feature requests.

Nestalgia is a work-in-progress emulator for NES and Famicom systems, built in Kotlin for Linux, macOS and Windows. It also emulates Famicom Disk System, Dendy, Vs. System, NSF and NSFe, and lists support for 305 mappers. The emulator includes save states, battery saves, overclocking and cheat codes, along with fullscreen display and screenshots. Audio, video, controller and emulation settings are configurable. More than 20 controllers are supported, including the NES Controller, Zapper, Power Pad and Four Score. The project lists passing CPU, video, audio, mapper and input accuracy tests. Windows, Linux and Mac downloads require Java 21 or newer. The project is free and open source under GPL-3.0, with no plan limits stated. Android is listed with an uncertain “Coming soon...or not :(” status. Developers can add its core library through JitPack using Gradle instructions. Nestalgia implements the emulator but does not include debugging tools.