Improved user experience. The new Java Plug-In starts applets in the background, so the web browser always remains responsive. Applets appear on the web page as they become ready to run.

The new Java Plug-In is designed to work in the following browsers:

* Internet Explorer 6 and 7 on Windows XP and Vista
* Firefox 3 on Windows XP, Windows Vista, Solaris and Linux

Note that the new Java Plug-In does not work in Firefox 2. On the Windows platform, when the new Java Plug-In is enabled via the Java Control Panel, launching Firefox 2 will use the classic plug-in and launching Firefox 3 will use the new plug-in. Sun Microsystems and the Mozilla Foundation have been working closely in order to support the new Java Plug-In in Firefox 3. Both organizations have mutually decided not to back-port the required changes — which are significant — to Firefox 2, as it is expected that most Firefox users will upgrade to Firefox 3 a short time after its final version has been released.