WebMSX

The people behind WebMSX

What WebMSX supports

• Runs in modern web browsers (Chrome, Firefox, Safari) on desktop and mobile
• Self-hostable on any static web hosting or simple HTTP server
• Can be embedded in webpages via the provided JavaScript API
• Loads ROM (.rom), disk (.dsk/.dmk), tape (.cas/.wav), Nextor hard-disk images, ZIP/GZIP-compressed images
• NetPlay (P2P) for multi-user shared sessions

Download and availability

WebMSX setup guide

1. Use the hosted emulator (fastest): Open https://webmsx.org in a modern browser (Chrome/Firefox/Safari). Use the UI to pick a machine or use URL query parameters to load media directly (for example: ?ROM=https://example.com/game.rom). The hosted instance provides the C-BIOS light set linked from the project site; do not expect commercial BIOS or commercial game ROMs to be bundled.
2. Download official releases: Go to the project's GitHub Releases page and download the desired release ZIP (release bundles are provided per tag). The releases include a release/stable folder with the distribution files suitable for hosting. Confirm the exact asset names in the release you download.
3. Self-hosting essentials: After extracting the release bundle, put the contents under any static HTTP(S) server root (Nginx, Apache, GitHub Pages, Netlify, S3 + CloudFront, etc.). No server-side code is required for basic use. Ensure the server serves correct MIME types for the JavaScript and asset files. If you intend to host NetPlay sessions or offer file hosting for remote ROMs, review the release notes and repository docs for any optional server components or recommended settings; NetPlay uses WebRTC and may require HTTPS for browser WebRTC features.
4. Build from source (optional): If you need to modify or rebuild the project, clone the GitHub repository. The repo contains package.json and a build process (grunt is present in repository files); you will need a Node.js toolchain (node and npm) and the development dependencies specified in package.json. Follow the repository's README and doc folder for exact build commands and release packaging steps.
5. Loading media and using URL parameters: WebMSX can load cartridges, disk/tape images, savestates, and configuration via URL query parameters or the global WMSX JavaScript object. Typical parameters include ROM, DISKA_URL, HARDDISK_URL, TAPE_URL, STATE_URL, PRESETS and MACHINE. Use the documented parameter names and file URLs; the emulator can auto-create disk images and accept ZIP/GZIP archives containing images.
6. Machine selection, extensions and BIOS: WebMSX provides many generic machine presets (MSX1, MSX2, MSX2+, MSX turbo R) and localized variants (NTSC/PAL, Japanese/European/American turbo R). Optional extensions like SCC, OPL4, MegaRAM, and Nextor hard-disk support are selectable from the UI or by preset. The project provides a light C-BIOS package for basic MSX booting; if your use requires specific commercial BIOS/firmware, you must obtain and supply those files yourself — they are not included.
7. Mobile and PWA use: The hosted site is designed as a Progressive Web App (PWA). On iOS and Android you can add it to the Home Screen and run it offline to the extent browser caching supports the release files. Expect limitations on some features (NetPlay uses WebRTC and may be restricted on some iOS versions).
8. NetPlay caution and performance: NetPlay is a peer-to-peer feature that uses WebRTC; performance depends on network latency and browser WebRTC support. For best results use desktop browsers with up-to-date WebRTC support and HTTPS. R800/ turbo R emulation and V9990/advanced sound/video support are more CPU-intensive — reduce turbo settings or select simpler machine models on low-power devices.

Sources and further reading

• Official GitHub repository (README, docs and release folders)
• GitHub Releases for WebMSX (release assets and tags)
• Official hosted emulator and documentation
• MSX Wiki entry for WebMSX (project summary)