The Storybook PostCSS addon can be used to run the PostCSS preprocessor against your stories in Storybook.

Install this addon by adding the @storybook/addon-postcss dependency:

yarn add -D @storybook/addon-postcss

within .storybook/main.js:

module.exports = {
  addons: ['@storybook/addon-postcss'],
};

and create a PostCSS config in the base of your project, like postcss.config.js, that contains:

module.exports = {
  // Add your installed PostCSS plugins here:
  plugins: [
    // require('autoprefixer'),
    // require('postcss-color-rebeccapurple'),
  ],
};

If your project requires you to be using PostCSS v8, you can replace the included PostCSS by passing postcssLoaderOptions to this addon.

First, you'll need to install PostCSS v8 as a dependency of your project:

yarn add -D postcss@^8

Then, you'll need to update your addons config. Within .storybook/main.js:

module.exports = {
  addons: [
-   '@storybook/addon-postcss',
+   {
+     name: '@storybook/addon-postcss',
+     options: {
+       postcssLoaderOptions: {
+         implementation: require('postcss'),
+       },
+     },
+   },
  ]
}

When running Storybook, you'll see the version of PostCSS being used in the logs. For example:

info => Using PostCSS preset with [email protected]

You can specify loader options for style-loader, css-loader, and postcss-loader by passing options to this addon as styleLoaderOptions, cssLoaderOptions, or postcssLoaderOptions respectively.

You can also configure the loader rule by overriding the rule option.