Rhino is a JavaScript engine written fully in Java and managed by the Mozilla Foundation as open source software.

Since then, a couple of major companies (including Sun Microsystems) have licensed Rhino for use in their products and paid Netscape to do so, allowing work to continue on it.

This produced the best performance, often beating the C++ implementation of JavaScript run with just-in-time compilation (JIT), but suffered from two faults.

Since its release to open source, Rhino has found a variety of uses and an increasing number of people have contributed to the code.

It is intended to be used in desktop or server-side applications, hence there is no built-in support for the Web browser objects that are commonly associated with JavaScript.