What is GWT? A set of tools to write AJAX applications in JAVA. GWT is an open source, cross-browser framework that allows developers to write AJAX applications in Java and get the bytecode compiled into JavaScript. What makes GWT interesting is Java to JavaScript compiler? GWT is more than just a Java-JavaScript Compiler. Based on the code that you write in Java, it performs dead code elimination, code optimization etc straightening polymorphic calls, method call in lining and string interning. basically the features of what a "compiler" does. Well why Java ? Because Java is a strongly typed language unlike python and that is when you get benefit of the compiler optimizations. But then again Java is the chosen one, because of the availability of IDE's, debugging tools etc and not that its the only best language in the world. Google didn't choose Java because of a particular attachment to the language, but because of the abundance of tools out there available for Java...