[[File:Jsmess in Chromium.png|thumb|upright=1.1|JSMESS emulating a CPC 6128 in Chromium 30 on Linux]]
MESS has also recently been ported to JavaScript using the C/C++-to-JS transcompiler Emscripten; this port is called [http://jsmess.textfiles.com/ JSMESS]. So far only a small selection of MESS machines are supported in JSMESS—the main problem is finding out which MESS modules are needed for a given architecture and creating the Makefiles accordingly, although JSMESS now includes scripts that scan for dependencies. A [https://github.com/mdoege/jsmess JSMESS fork] that includes the necessary Makefiles to build the CPC 6128 version exists. (It is recommended to build JSMESS on Linux (which also makes it easier to install the dependencies for Emscripten.).
A [https://github.com/mdoege/jsmess JSMESS fork] that includes the necessary Makefiles to build the CPC 6128 version exists. Note that the ROM file cpc6128.zip also needs to contain the AMSDOS ROM files from cpc464.zip because unlike regular MESS, JSMESS only loads a single ROM ZIP file per machine.
As of October 2013, sound only works in Firefox and not in Chrome/Chromium. Also, keymapping has not been done for JSMESS systems, although in principle you should be able to create keymaps in MESS and use them with JSMESS. The joystick is mapped to Alt and the arrow keys by default.