Minification (programming)

Minification (also minimisation or minimization), in computer programming languages and especially JavaScript, is the process of removing all unnecessary characters from source code without changing its functionality. These unnecessary characters usually include white space characters, new line characters, comments, and sometimes block delimiters, which are used to add readability to the code but are not required for it to execute.

Minified source code is especially useful for interpreted languages deployed and transmitted on the Internet (such as JavaScript), because it reduces the amount of data that needs to be transferred. Minified source code may also be used as a kind of obfuscation, though the term obfuscation may be distinguished as a form of false cryptography while a minified code instance may be reversed using a pretty-printer. In programmer culture, aiming at extremely minified source code is the purpose of recreational code golf competitions.

Minification can be distinguished from the more general concept of data compression in that the minified source can be interpreted immediately without the need for an uncompression step: the same interpreter can work with both the original as well as with the minified source.

For example the JavaScript script

is equivalent to but longer than

In 2003 Douglas Crockford introduced tool JSMin, which only removed comments and whitespace. It was followed by YUI Compressor shortly thereafter. In 2009, Google opened up its Closure toolkit, including Closure Compiler which contained a source mapping feature together with a Firefox extension called Closure Inspector. In 2010, Mihai Bazon introduced UglifyJS, which was superseded by UglifyJS2 in 2012; the rewrite was to allow for source map support.

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