postcss

Process CSS file

$ postcss [input.css] -o [output.css]

$ postcss [input.css] -o [output.css] -c [postcss.config.js]

$ postcss [input.css] -o [output.css] --watch

$ postcss [src/] -d [dist/]

$ postcss [input.css] -o [output.css] -u [autoprefixer]

$ postcss [style.css] --replace

$ postcss [input.css] -o [output.css] --map

postcss [-o output] [-d dir] [-c config] [-u plugins] [options] files

postcss is a tool for transforming CSS with JavaScript plugins. Rather than being a preprocessor itself, it provides a framework where plugins perform specific transformations on the CSS abstract syntax tree. Popular plugins include Autoprefixer for adding vendor prefixes, cssnano for minification, and postcss-preset-env for using future CSS syntax today.
Plugins are chained together in a configuration file (postcss.config.js) or specified on the command line. Each plugin receives the parsed CSS, applies its transformation, and passes the result to the next plugin. This modular approach allows teams to compose exactly the processing pipeline they need.
Watch mode reprocesses files automatically when changes are detected, integrating into development workflows. Source maps preserve the mapping between transformed and original CSS for debugging in browser developer tools.

-o, --output FILE

Output file.

Output directory.

Config file path.

Plugins to use.

Watch mode.

Generate source maps.

Replace input files.

Disable source maps.

Verbose output.

postcss.config.js (or .postcssrc, postcss.config.mjs)

Plugin configuration file defining the processing pipeline. Lists plugins in order with their options. Searched upward from the input file directory.

Alternative location for PostCSS configuration within the project manifest.

Requires plugins for functionality. Node.js environment. Config complexity can grow.

PostCSS was created by Andrey Sitnik in 2013. It pioneered CSS-as-AST transformation and hosts a rich plugin ecosystem.

sass(1), less(1), autoprefixer(1), cssnano(1)