# [postcss][postcss]-unique-selectors > Ensure CSS selectors are unique. ## Install With [npm](https://npmjs.org/package/postcss-unique-selectors) do: ``` npm install postcss-unique-selectors --save ``` ## Example Selectors are sorted naturally, and deduplicated: ### Input ```css h1,h3,h2,h1 { color: red } ``` ### Output ```css h1,h2,h3 { color: red } ``` ## Usage See the [PostCSS documentation](https://github.com/postcss/postcss#usage) for examples for your environment. ## Contributors See [CONTRIBUTORS.md](https://github.com/cssnano/cssnano/blob/master/CONTRIBUTORS.md). ## License MIT © [Ben Briggs](http://beneb.info) [postcss]: https://github.com/postcss/postcss