yuicompressor

The Yahoo! JavaScript and CSS Compressor

YUI Compressor is JavaScript and CSS minificator. YUI Compressor is written in Java and relies on Rhino to tokenize the source JavaScript file. It starts by analyzing the source JavaScript file to understand how it is structured. It then prints out the token stream, omitting as many white space characters as possible, and replacing all local symbols by a 1 (or 2, or 3) letter symbol wherever such a substitution is appropriate (in the face of evil features such as eval or with, the YUI Compressor takes a defensive approach by not obfuscating any of the scopes containing the evil statement). The CSS compression algorithm uses a set of finely tuned regular expressions to compress the source CSS file. The YUI Compressor is open-source, so don't hesitate to look at the code to understand exactly how it works.