JSMoo

Spec sheet

Purpose

JSMoo is an attempt to make accurate, performant retro-system emulators in JavaScript and AssemblyScript.Read 11 Oct 2026 · github.com

License

The repository says JSMoo is distributed under the MIT License.Read 11 Oct 2026 · github.com

BIOS requirement

Sega Master System and ZX Spectrum require BIOS files, which can be uploaded under Settings/BIOS.Read 11 Oct 2026 · github.com

Browser use

JSMoo runs in a browser and the README recommends Chrome for speed.Read 11 Oct 2026 · github.com

Known limitation

The README says ZX Spectrum keyboard input was temporarily broken at the time of that commit.Read 11 Oct 2026 · github.com

Learning focus

The maker says the project aims to make vintage systems and processors easier for people to play and understand, including through planned Easy6502-like learning pages.Read 11 Oct 2026 · github.com

Local setup

The README instructs users to clone the repository, run its Python 3 server script, and open the local address in Chrome.Read 11 Oct 2026 · github.com

ROM and controls

Users can upload ROM files and remap controls in the Settings tab.Read 11 Oct 2026 · github.com

SNES emulation

The README describes cycle-accurate 65816 emulation, not-quite-cycle-accurate SPC700 emulation, scanline-based PPU rendering, and no DSP emulation in its proof of concept.Read 11 Oct 2026 · github.com

Support and contributions

The maker invites bug fixes, optimizations, cleanup, and other improvements through GitHub forks and pull requests.Read 11 Oct 2026 · github.com

Supported systems

The project describes current support for SNES, NES, Game Boy, Sega Master System, ZX Spectrum, and Game Gear.Read 11 Oct 2026 · github.com

Technical requirements

The project uses SharedArrayBuffers and high-precision timers, so it requires special HTTP headers and cannot be run by opening index.html directly from disk.Read 11 Oct 2026 · github.com

Plans and prices

Every JSMoo plan and price →

Where Specifiction places it

• Multi-System Emulators#40 of 547.4