Stopify will support long-running L programs without freezing the browser tab. In particular, programs can access the DOM and are not limited to Web Workers.
Stopify can pause or terminate an L program, even if it is an infinite loop.
Stopify can set breakpoints or single-step through the L program, if C generates source maps.
Stopify can simulate an arbitrarily deep stack and proper tail calls. This feature is necessary to run certain functional programs in the browser.
Stopify can simulate blocking operations on the web.
To learn how to use Stopify in your own project, see the Stopify Wiki.