Firefox 3 uses SpiderMonkey engine to optimize JavaScript treatment speed. Version 3 of the famous fire fox was already 3 times faster than version 2 of the browser. The Mozilla Foundation promises a treatment 30 to 40 times faster now with the introduction of TraceMonkey interpreter in this version 3.1 of Firefox.

TraceMonkey will then complete SpiderMonkey by adding the possibility of recording the JavaScript execution engine and allowing it to be automatically compiled in a similar future usage.

TraceMonkey will also be integrated into Firefox version 4; it will integrate Adobe's virtual machine, ActionScript.