---
id: post-processing-css
title: Post-Processing CSS
---

This project setup minifies your CSS and adds vendor prefixes to it automatically through [Autoprefixer](https://github.com/postcss/autoprefixer) so you don’t need to worry about it.

Support for new CSS features like the [`all` property](https://developer.mozilla.org/en-US/docs/Web/CSS/all), [`break` properties](https://www.w3.org/TR/css-break-3/#breaking-controls), [custom properties](https://developer.mozilla.org/en-US/docs/Web/CSS/Using_CSS_variables), and [media query ranges](https://www.w3.org/TR/mediaqueries-4/#range-context) are automatically polyfilled to add support for older browsers.

You can customize your target support browsers by adjusting the `browserslist` key in `package.json` according to the [Browserslist specification](https://github.com/browserslist/browserslist#readme).

For example, this:

```css
.App {
  display: flex;
  flex-direction: row;
  align-items: center;
}
```

becomes this:

```css
.App {
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-orient: horizontal;
  -webkit-box-direction: normal;
  -ms-flex-direction: row;
  flex-direction: row;
  -webkit-box-align: center;
  -ms-flex-align: center;
  align-items: center;
}
```

If you need to disable autoprefixing for some reason, [follow this section](https://github.com/postcss/autoprefixer#disabling).

[CSS Grid Layout](https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Grid_Layout) prefixing is disabled by default, but it will **not** strip manual prefixing.
If you'd like to opt-in to CSS Grid prefixing, [first familiarize yourself about its limitations](https://github.com/postcss/autoprefixer#does-autoprefixer-polyfill-grid-layout-for-ie).<br>
To enable CSS Grid prefixing, add `/* autoprefixer grid: autoplace */` to the top of your CSS file.