Closure Compiler is a JavaScript optimizer that compiles web apps down into compact, high-performance JavaScript code. The compiler removes dead code, then rewrites and minimizes what’s left so that it will run fast on browsers’ JavaScript engines. The compiler also checks syntax, variable references, and types, and warns about other common JavaScript pitfalls. These checks and optimizations help you write apps that are less buggy and easier to maintain. You can use the compiler with Closure Inspector, a Firebug extension that makes debugging the obfuscated code almost as easy as debugging the human-readable source.

Because JavaScript developers are a diverse bunch, we’ve set up a number of ways to run the Closure Compiler. We’ve open-sourced a command-line tool. We’ve created a web application that accepts your code for compilation through a text box or a RESTful API. We are also offering a Firefox extension that you can use with Page Speed to conveniently see the performance benefits for your web pages.

via Google Code Blog: Introducing Closure Tools.