Browsix: Unix in the browser tab:
https://browsix.org/ [browsix.org]

(best to go with their description):

Browsix is a framework that bridges the considerable gap between conventional operating systems and the browser, enabling unmodified programs expecting a Unix-like environment to run directly in the browser. Browsix does this by mapping low-level Unix primitives, like processes and system calls, onto existing browser APIs, like Web Workers [developer.mozilla.org] and postMessage [developer.mozilla.org]. Browsix brings all of these abstractions into unmodified browsers, and is isolated and secured to the same extent any normal web page is: at the level of the browser tab.
To use Browsix, client-side JavaScript code creates an instance of a Browsix kernel (which involves telling it how to initialize the filesystem), and then asks the kernel to start or kill processes.

Browsix is a research project from the PLASMA lab [plasma.cs.umass.edu] at the University of Massachusetts, Amherst.


the javascript in the examples provided is in the 100s of KB, but a ~1MB page size might be appropriate for some applications.
it will be interesting to see how well this works - i'm thinking mostly of filesystem and memory management issues here.


also note this related WebmasterWorld post in the Search Engine Spider and User Agent Identification forum - Browsix [webmasterworld.com]