WebMSX, or simply WMSX, is a new cross platform MSX emulator designed for the Web.

WebMSX is great for displaying MSX software running inside webpages. You can launch the emulator and load ROMs, DSK and CAS images with a single link. Join friends in multiplayer games or pair programming sessions with the new NetPlay! function.

Please go to https://webmsx.org to enjoy it online!

Refer to /doc for parameters reference and URL usage examples. Refer to /release for stable release files and deployment examples.

MSX and the MSX logo are shown here as a tribute. All trademarks are property of their respective owners.

• 3 MSX turbo R machines (Japanese, European, American)
• V9990 video, Superimposed and Mixed modes, or Dual Screens
• Improved CPU Turbo emulation and control, Z80/R800 speed settings
• Improved Kanji support, with MSX-JE input editor and dictionary
• 6 MSX1 Palettes. Color, B&W, Green and Amber CRTs with scanlines
• New AZERTY key mapping. Simplified hotkeys

• 12 Generic machines (MSX1, MSX2, MSX2+, MSX tR). NTSC 60Hz or PAL 50Hz
• V9918, V9938, V9958 and V9990 video, Superimposing, Mixed, Dual Screen modes
• PSG, SCC, SCC-I, FM-PAC, PCM, MSX-MUSIC and OPL4-Wave sound
• Kanji support, with MSX-JE Japanese text input editor and dictionary
• Cross platform HTML5/JS. Runs in any Browser, tested in Chrome/Firefox/Safari
• Show MSX software running on any webpage, or with a link to the WebMSX page
• Finally enjoy MSX games on your iPhone/iPad! Installs as a WebApp, runs offline
• Open files from local storage, iCloud, Google Drive, Dropbox, web links
• NetPlay! Connect several users on the same Virtual MSX machine over the internet
• CPU and VDP Turbo modes up to 8x, with manual or software activation
• Load Cartridge ROMs, HardDisk (Nextor), Disk and Tape images
• Powerful Drag & Drop system for loading media files
• Dynamically import files to any MSX disk drive, automatic image creation
• Savestates support. Export and share Savestate files and links
• Customizable Keyboard, Joysticks, Joykeys, and Mouse controllers
• Customizable Touch Controls/Virtual Keyboard for mobile devices (iOS, Android)
• Joykeys support. Emulates MSX Joysticks using Host Keyboard
• Virtual buttons. Maps Host Joystick buttons to MSX Keyboard keys
• Easily toggle extensions like SCC+, SCC, PAC, MegaRAM, Nextor, DoublePSG, etc.
• Adjustable speed, Pause and Frame-by-frame advance
• PSG/SCC/OPLL Stereo Sound simulation, configurable
• Copy & Paste text, Screen Capture, Debug modes
• CRT Scanlines, resizable Screen, Full Screen and Full Windowed modes
• 6 MSX1 Palettes. Color, B&W, Green and Amber phosphor simulation
• Javascript API for loading media and machine control

We still have some limitations on the tR and R800 emulation in this release. There is no PCM and MIDI support yet, and R800 CPU advanced timing may not be completely accurate. Also, R800 emulation hits very hard on the emulator performance, so it may not run smoothly on all devices, specially smartphones. There are options to tweak the R800 timing and clock speed from 0.5x to 2.0x.

The current V9990 implementation also has some limitations on the Command Termination and Horizontal INTs. But none of the available/tested software seemed to rely on the incomplete functions.

The light version with only C-BIOS ROMs can be found at: https://webmsx.org/cbios

WebMSX 5.0 brings NetPlay!, in which any number of users may connect and control the same virtual MSX machine. To access the feature, open the NetPlay! control dialog available on the System Menu (Power button).

One user must be the "Server" and start a NetPlay! Session. Just choose a name for the Session, or let the emulator generate it randomly, then hit "START". Once the Session is started and active, other users may join the Session simply by entering the same Session name and hitting "JOIN". All users connected have complete control over the machine, except that only the Server user may load/change media files (ROMs, Disks, etc). All features of the emulator work during NetPlay! Any Client user may leave the Session at any time, but only the Server user may end the Session completely.

Be careful not to make your Session name public! Anyone that knows your Session name will be able to join it while its active. Send the session name only to people you want to invite. Another way of sharing your Session to users is sending them a link that will open the emulator and join the session automatically. In the NetPlay! dialog, once you are Hosting a Session, there will be a link button on the upper right, that will generate the link and copy it to your clipboard.

IMPORTANT: NetPlay! performance is completely dependent on the network quality. The lower the network latency between users, the better. Higher bandwidths with higher latencies won't help much. The Client may need some time to find and connect do the Server. It uses a specialized P2P protocol, and tries to use STUN to traverse NATs/routers so users don't have to worry about IPs and opening ports. Use at your own risk! :-)

To make all this work seamlessly, WebMSX uses modern Web technologies including WebRTC, which are supported by all major browsers and platforms. Unfortunately, those technologies may still not be available on Apple iOS, so NetPlay! may not work on those devices.

To make the Hard Disk Drive available, you must first activate the Hard Drive Extension, through the Extensions Menu on the user interface, or by using the respective Presets. The Hard Disk device may be placed "before" the Floppy Drives, so it will appear on the system as Drive A, or "after" the Floppy Drives, so it will appear as Drive C. The position depends on which Slot the Extension is activated on. If using Presets, there are two available: HARDDISK will place the device as Drive A, and HARDDISKC will place it as Drive C. On the Hard Drive menu (HD icon), there are options to automatically create Empty and Boot disks of several sizes. You can also load DSK images, Files or ZIPs normally.

Several parameters are available for customizing the emulator. They can be changed either directly in Javascript if you are hosting the emulator in your own page, by loading a Configuration File, or via URL Query Parameters if you are creating links or bookmarks to open the emulator, or just using it in your browser.

All parameters are in the form of properties in the global object WMSX. Just set these object properties in Javascript, or use URL Query parameter/value pairs. For example:

WMSX.ROM = "files/Game.rom";      is the same as      https://webmsx.org?ROM=files/Game.rom

To load an external Configuration File, set the CONFIG_URL parameter. The config file must be a valir JSON object. This object's properties will be merged with the standard configuration properties. For example:

WMSX.CONFIG_URL = "files/CustomMachines.json";     or     https://webmsx.org?CONFIG_URL=files/CustomMachines.json

All emulator Savestates, Settings and Preferences can be stored in multiple isolated spaces, using the Environments feature. Just set the ENVIRONMENT parameter (or E for short) to any number in the 1..99 range. For example:

WMSX.ENVIRONMENT = 2;     or     https://webmsx.org?E=2

Another important concept is the use of configuration Presets. Some configurations are a bit complicated and may require setting various parameters in conjunction. For those cases, its easier to use a Preset that will automatically set all the relevant parameters for a specific task. You may specify any number of Presets to be used by setting the PRESETS parameter (or P for short) with a comma separated list of the Preset names to apply. For example:

WMSX.PRESETS = "RAM128, NODISK";     or     https://webmsx.org?P=RAM128,NODISK

IMPORTANT: Any parameter setting via Javascript must be done AFTER importing the webmsx.js file.

The emulator can be set to automatically load files like ROMs, DSK and CAS images. Additionally, files can be loaded and automatically injected into any of the Disks Drives, without having to first create an image. Image files may be compressed in ZIP or GZIP formats. If several Disk images are found in a ZIP file, all of them (up to 10) will be loaded in the Drive Stack. Available parameters:

The ROM Format is auto-detected. To force a format, set the CARTRIDGE1_FORMAT and CARTRIDGE2_FORMAT parameters, or access the User Interface. You can also put the format specification in the ROM file name, between brackets. Example: Game [KonamiSCC].rom

Normal, Mirrored, NotMirrored, ASCII8, ASCII16, Konami, KonamiSCC, KonamiSCCI, ASCII8SRAM2, ASCII8SRAM8, ASCII16SRAM2, ASCII16SRAM8, MegaRAM, GameMaster2, KoeiSRAM8, KoeiSRAM32, Wizardry, FMPAC, FMPAK, MSXDOS2, Majutsushi, Synthesizer, RType, CrossBlaim, Manbow2, HarryFox, AlQuran, AlQuranDecoded, Halnote, SuperSwangi, SuperLodeRunner, Dooly, Zemina80in1, Zemina90in1, Zemina126in1, MSXWrite, KonamiUltimateCollection

There are 12 different generic machines. The default machine is the MSX2+, and the emulator will try to auto-detect your region. You can ask for a specific machine by setting the MACHINE parameter (or M for short) with the respective Machine ID:

It's possible to define additional Custom Machines, by loading an external Configuration File (CONFIG_URL parameter). Contact the author for details!

The emulator supports several Extensions, or optional components that can be turned on/off. Some are in the form of expansion cartridges that can be inserted in either Slot 1 or 2. We use Presets to make configuring Extensions easier:

The emulator can be set to automatically Run/Load BASIC programs after launch, or type any commands or text in the BASIC prompt. NOTE that these are not necessary for AUTOEXEC.BAS and AUTOEXEC.BAT files, or if you have loaded a Tape Image file (in which case the emulator will automatically detect and Run the first program in the Tape). Available parameters:

WebMSX is great for displaying MSX software in the web. With a simple URL, you can launch the emulator and automatically load and run anything. You may combine several settings and media loading options in a single link. Here are some examples:

• To load a game in ROM format:

https://webmsx.org?ROM=https://gamesarchive.org/Goonies.rom

• To load a game in a ZIPped Disk Image and insert a SCC+ Sound Cartridge:

https://webmsx.org?DISK=https://gamesarchive.org/SDSnatcher.zip&PRESETS=SCCI

• To launch an European MSX1 machine, loading a Disk image and then run a BASIC program:

https://webmsx.org?MACHINE=MSX1E&DISK=https://basicmuseum.org/Demos.dsk&BASIC_RUN=Bubbles.bas