PostCSS Base Plugin lets you easily create new plugins following some CSS Specification.

.foo {
	color: red;
}

.baz {
	color: green;
}

/* becomes */

.foo {
	color: blue;
}

.baz {
	color: green;
}

Add PostCSS Base Plugin to your project:

npm install postcss @csstools/postcss-base-plugin --save-dev

Use it as a PostCSS plugin:

const postcss = require('postcss');
const postcssBasePlugin = require('@csstools/postcss-base-plugin');

postcss([
	postcssBasePlugin(/* pluginOptions */)
]).process(YOUR_CSS /*, processOptions */);

PostCSS Base Plugin runs in all Node environments, with special instructions for:

• Node
• PostCSS CLI
• PostCSS Load Config
• Webpack
• Next.js
• Gulp
• Grunt

The preserve option determines whether the original notation is preserved. By default, it is not preserved.

postcssBasePlugin({ preserve: true })

.foo {
	color: red;
}

.baz {
	color: green;
}

/* becomes */

.foo {
	color: blue;
	color: red;
}

.baz {
	color: green;
}