PostCSS Nesting lets you nest style rules inside each other, following the CSS Nesting specification.

If you want nested rules the same way Sass works you might want to use PostCSS Nested instead.

.foo {
	color: red;

	&:hover {
		color: green;
	}

	> .bar {
		color: blue;
	}

	@media (prefers-color-scheme: dark) {
		color: cyan;
	}
}

/* becomes */

.foo {
	color: red;
}
.foo:hover {
		color: green;
	}
.foo > .bar {
		color: blue;
	}
@media (prefers-color-scheme: dark) {
	.foo {
		color: cyan;
}
	}

Add PostCSS Nesting to your project:

npm install postcss postcss-nesting --save-dev

Use it as a PostCSS plugin:

const postcss = require('postcss');
const postcssNesting = require('postcss-nesting');

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

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

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

Previous iterations of the CSS Nesting specification required using @nest for certain selectors.

@nest was removed from the specification completely. Future versions of this plugin will error if you use @nest.

We advice everyone to migrate their codebase now to nested CSS without @nest.
We published a Stylelint Plugin to help you migrate.

example warning:

@nest was removed from the CSS Nesting specification and will be removed from PostCSS Nesting in the next major version. Change @nest foo & {} to foo & {} to migrate to the latest standard.

You can silence this warning with a new silenceAtNestWarning plugin option.

postcssNesting({
	silenceAtNestWarning: true
})

Before :

#alpha,
.beta {
	&:hover {
		order: 1;
	}
}

After without the option :

postcssNesting()

:is(#alpha,.beta):hover {
	order: 1;
}

.beta:hover has specificity as if .beta where an id selector, matching the specification.

specificity: 1, 1, 0

After with the option :

postcssNesting({
	noIsPseudoSelector: true
})

#alpha:hover, .beta:hover {
	order: 1;
}

.beta:hover has specificity as if .beta where a class selector, conflicting with the specification.

specificity: 0, 2, 0

Before :

.alpha > .beta {
	& + & {
		order: 2;
	}
}

After without the option :

postcssNesting()

:is(.alpha > .beta) + :is(.alpha > .beta) {
	order: 2;
}

After with the option :

postcssNesting({
	noIsPseudoSelector: true
})

.alpha > .beta + .alpha > .beta {
	order: 2;
}

this is a different selector than expected as .beta + .alpha matches .beta followed by .alpha.
avoid these cases when you disable :is()
writing the selector without nesting is advised here

/* without nesting */
.alpha > .beta + .beta {
	order: 2;
}