minification

Minification is the process of removing all nonessential characters from source code or markup to reduce file size without changing its observable behavior. It is commonly applied to JavaScript, CSS, HTML, and sometimes JSON or other textual resources. The primary goal is to decrease bandwidth usage and improve page load times and performance, especially on slow networks and mobile devices.

Minification achieves size reduction by eliminating whitespace, line breaks, comments, and sometimes optional punctuation. Many minifiers also shorten variable and function names through name mangling or other transformations, which can reduce code size further. It is designed to be semantics-preserving, meaning the minified code should behave the same as the original in all typical runtimes, though debugging may become harder without mapping information.

Minification is distinct from general compression. Minification operates on the source text before transmission, whereas compression (such as gzip) compresses the already minified text for server delivery. In practice, both techniques are used together: source files are minified, then compressed for network transfer. Source maps can be generated to help developers map errors from the minified code back to the original source.

Common tools include JavaScript minifiers like Terser and UglifyJS; CSS minifiers such as cssnano; and HTML minifiers like html-minifier. Build tools and bundlers (for example, Webpack or Rollup) automate minification during production builds. Developers should balance minification with debugging needs and enable source maps in development; care should be taken with dynamic code or code relying on exact formatting.