Nostalgist.js

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What Nostalgist.js is

Nostalgist.js is a free JavaScript library for developers building retro console emulation experiences in web browsers. It simplifies starting RetroArch with a ROM and a core, without extra configuration. The library does not contain emulators; by default, it fetches cores from RetroArch Emscripten builds through jsDelivr. Developers can adjust RetroArch and core settings before launch, and the API exposes lower-level Emscripten interfaces such as the virtual filesystem. Games can save a state and load it later. Documented helpers cover NES, SNES, Mega Drive, Game Boy, Game Boy Color, and Game Boy Advance. Developers can install the library through npm, yarn, pnpm, or bun, or load it from unpkg and jsDelivr. ROM files can be served from a developer's own server, which needs correctly configured CORS headers. The project does not provide or encourage pirated ROM or BIOS files. Nostalgist.js is MIT licensed, supports web browsers, and has no paid plans stated. Its showcases include a StackBlitz example, NextCloud Nostalgist, and a VS Code extension.

Who it suits

It suits developers who want to build browser-based emulation experiences and configure RetroArch or its cores. Developers supplying ROM files from their own server need to configure CORS headers.

What it does well

Free and MIT licensed
Supports save and load states
Helpers cover six console families
Installable through four package managers

What to know first

The library does not include emulators
ROM hosting requires correctly configured CORS headers
Web browsers are the listed platform

Limits

Nostalgist.js does not include emulator cores; they are fetched by default from RetroArch Emscripten builds via jsDelivr. ROM files hosted on your own server require correctly configured CORS headers.

Plans

Plan	Billed and limits	Price
Nostalgist.js	MIT-licensed JavaScript library; no paid plans are stated	Free
Free open-source library	Browser-based retro emulation · developer-focused · ROMs and BIOS supplied by integrator	Free

As nostalgist.js.org lists them, read 4 Oct 2026. The maker's own page has the final word.

Getting started

Open https://nostalgist.js.org/ for the project information.
Add the library to a project using npm, yarn, pnpm, or bun, or load it from unpkg or jsDelivr.
Provide a ROM file from your own server with CORS headers configured properly.
Configure RetroArch and core settings if needed, then launch with a ROM and core.

Verdict

Nostalgist.js provides a developer-facing way to launch browser-based RetroArch emulation and configure related settings. Developers need to supply ROM content and account for the library's separate core delivery.

Questions

How much does Nostalgist.js cost?

The listed plan is free. No paid plans are stated.

Which platforms does it support?

It supports web browsers.

Does Nostalgist.js include emulator cores?

No. By default, cores are fetched from RetroArch Emscripten builds via jsDelivr.

Can it save game progress?

Yes. The library can save a game's state and load it later.

Is Nostalgist.js open source?

The GitHub repository identifies the project as MIT licensed.

How can developers add it to a project?

It can be installed through npm, yarn, pnpm, or bun, or loaded from unpkg or jsDelivr.

Facts from Nostalgist.js's own pages

BIOS loading: BIOS files use the same resolvable-file mechanism as ROMs and are written to RetroArch’s system directory. · nostalgist.js.org, 15 Oct 2026
Bring your own content: Developers can load ROM files from their own server, which must have CORS headers configured properly. · nostalgist.js.org, 4 Oct 2026
Cheat support: The launch API documents cheat codes, but they require RetroArch 1.21.0-or-later cores that implement cheats. · nostalgist.js.org, 15 Oct 2026
Configuration: Developers can customize RetroArch and core configuration before launch. · nostalgist.js.org, 4 Oct 2026
Console helpers: Documented shortcut methods cover NES, SNES, Mega Drive, Game Boy, Game Boy Color and Game Boy Advance. · nostalgist.js.org, 15 Oct 2026
Content limitation: The project says it does not provide or encourage pirated ROM or BIOS files. · nostalgist.js.org, 4 Oct 2026
Content policy: The project says it does not provide or encourage pirated ROM or BIOS files. · nostalgist.js.org, 15 Oct 2026
Core delivery: String core names default to RetroArch Emscripten builds fetched from GitHub through jsDelivr. · nostalgist.js.org, 15 Oct 2026
CORS requirement: ROMs hosted on a developer’s server require correctly configured CORS headers. · nostalgist.js.org, 15 Oct 2026
Custom cores: Developers can provide custom JavaScript and WebAssembly core URLs or resolver functions. · nostalgist.js.org, 15 Oct 2026
Dependencies and delivery: Nostalgist.js itself does not contain emulators; by default, emulator cores are fetched from RetroArch Emscripten builds via jsDelivr. · nostalgist.js.org, 4 Oct 2026
Developer audience: The project is intended for developers building browser experiences rather than players seeking a ready-made game collection. · nostalgist.js.org, 15 Oct 2026
Distribution: Projects can install the library through npm, yarn, pnpm, or bun, or load it from CDNs including unpkg and jsDelivr. · nostalgist.js.org, 4 Oct 2026
Documentation depth: The official site provides getting-started, under-the-hood and API-reference sections with static and instance method documentation. · nostalgist.js.org, 15 Oct 2026
Emscripten access: The library exposes lower-level Emscripten interfaces, including the virtual filesystem. · nostalgist.js.org, 15 Oct 2026
Emulation engine: It simplifies launching RetroArch in a browser using a ROM and a core, without additional configuration. · nostalgist.js.org, 4 Oct 2026
Examples and integrations: The project documents a StackBlitz example and lists projects including NextCloud Nostalgist and a VS Code extension among its showcases. · nostalgist.js.org, 4 Oct 2026
Independent extension: The PyPI Sphinx extension embeds NostalgistJS in HTML documents and maps Mega Drive, NES, SNES and Game Boy families to named cores. · pypi.org, 15 Oct 2026
Independent integration: The MD Have Fun web emulator states that it is built with RetroArch and Nostalgist.js and supports Chrome, Firefox and Edge. · msdk316.uk, 15 Oct 2026
Independent integration: controls: MD Have Fun lists keyboard controls and beta mobile touch controls for its Nostalgist.js-powered emulator. · msdk316.uk, 15 Oct 2026
Independent praise: ecosystem: MEDevel highlights projects built with Nostalgist.js, including RetroAssembly, vme, NextCloud Nostalgist and VS Code tooling. · medevel.com, 15 Oct 2026
Independent praise: usability: MEDevel describes launching a retro game with a small amount of browser code and praises the combination of simplicity and developer control. · medevel.com, 15 Oct 2026
Independent praise: WebAssembly: MEDevel reports that the library runs NES, SNES and Sega Genesis emulators in browsers using WebAssembly. · medevel.com, 15 Oct 2026
Input limitation: The press API states that analog joysticks are not currently supported. · nostalgist.js.org, 15 Oct 2026

Where Nostalgist.js stands on Freedom251

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