| --- |
| title: How to configure PostCSS in Next.js |
| nav_title: PostCSS |
| description: Extend the PostCSS config and plugins added by Next.js with your own. |
| --- |
|
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| |
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| Next.js compiles CSS for its [built-in CSS support](/docs/app/getting-started/css) using PostCSS. |
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| Out of the box, with no configuration, Next.js compiles CSS with the following transformations: |
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| - [Autoprefixer](https://github.com/postcss/autoprefixer) automatically adds vendor prefixes to CSS rules (back to IE11). |
| - [Cross-browser Flexbox bugs](https://github.com/philipwalton/flexbugs) are corrected to behave like [the spec](https://www.w3.org/TR/css-flexbox-1/). |
| - New CSS features are automatically compiled for Internet Explorer 11 compatibility: |
| - [`all` Property](https://developer.mozilla.org/docs/Web/CSS/all) |
| - [Break Properties](https://developer.mozilla.org/docs/Web/CSS/break-after) |
| - [`font-variant` Property](https://developer.mozilla.org/docs/Web/CSS/font-variant) |
| - [Gap Properties](https://developer.mozilla.org/docs/Web/CSS/gap) |
| - [Media Query Ranges](https://developer.mozilla.org/docs/Web/CSS/Media_Queries/Using_media_queries |
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| By default, [CSS Grid](https://www.w3.org/TR/css-grid-1/) and [Custom Properties](https://developer.mozilla.org/docs/Web/CSS/var) (CSS variables) are **not compiled** for IE11 support. |
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| To compile [CSS Grid Layout](https://developer.mozilla.org/docs/Web/CSS/grid) for IE11, you can place the following comment at the top of your CSS file: |
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| ```css |
| /* autoprefixer grid: autoplace */ |
| ``` |
|
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| You can also enable IE11 support for [CSS Grid Layout](https://developer.mozilla.org/docs/Web/CSS/grid) |
| in your entire project by configuring autoprefixer with the configuration shown below (collapsed). |
| See ["Customizing Plugins"]( |
|
|
| <details> |
| <summary>Click to view the configuration to enable CSS Grid Layout</summary> |
|
|
| ```json filename="postcss.config.json" |
| { |
| "plugins": [ |
| "postcss-flexbugs-fixes", |
| [ |
| "postcss-preset-env", |
| { |
| "autoprefixer": { |
| "flexbox": "no-2009", |
| "grid": "autoplace" |
| }, |
| "stage": 3, |
| "features": { |
| "custom-properties": false |
| } |
| } |
| ] |
| ] |
| } |
| ``` |
|
|
| </details> |
|
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| CSS variables are not compiled because it is [not possible to safely do so](https://github.com/MadLittleMods/postcss-css-variables |
| If you must use variables, consider using something like [Sass variables](https://sass-lang.com/documentation/variables) which are compiled away by [Sass](https://sass-lang.com/). |
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| Next.js allows you to configure the target browsers (for [Autoprefixer](https://github.com/postcss/autoprefixer) and compiled css features) through [Browserslist](https://github.com/browserslist/browserslist). |
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| To customize browserslist, create a `browserslist` key in your `package.json` like so: |
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| ```json filename="package.json" |
| { |
| "browserslist": [">0.3%", "not dead", "not op_mini all"] |
| } |
| ``` |
|
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| You can use the [browsersl.ist](https://browsersl.ist/?q=%3E0.3%25%2C+not+ie+11%2C+not+dead%2C+not+op_mini+all) tool to visualize what browsers you are targeting. |
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| No configuration is needed to support CSS Modules. To enable CSS Modules for a file, rename the file to have the extension `.module.css`. |
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| You can learn more about [Next.js' CSS Module support here](/docs/app/getting-started/css). |
| |
| ## Customizing Plugins |
| |
| > **Warning**: When you define a custom PostCSS configuration file, Next.js **completely disables** the [default behavior](#default-behavior). |
| > Be sure to manually configure all the features you need compiled, including [Autoprefixer](https://github.com/postcss/autoprefixer). |
| > You also need to install any plugins included in your custom configuration manually, i.e. `npm install postcss-flexbugs-fixes postcss-preset-env`. |
| |
| To customize the PostCSS configuration, create a `postcss.config.json` file in the root of your project. |
| |
| This is the default configuration used by Next.js: |
| |
| ```json filename="postcss.config.json" |
| { |
| "plugins": [ |
| "postcss-flexbugs-fixes", |
| [ |
| "postcss-preset-env", |
| { |
| "autoprefixer": { |
| "flexbox": "no-2009" |
| }, |
| "stage": 3, |
| "features": { |
| "custom-properties": false |
| } |
| } |
| ] |
| ] |
| } |
| ``` |
| |
| > **Good to know**: Next.js also allows the file to be named `.postcssrc.json`, or, to be read from the `postcss` key in `package.json`. |
| |
| It is also possible to configure PostCSS with a `postcss.config.js` file, which is useful when you want to conditionally include plugins based on environment: |
| |
| ```js filename="postcss.config.js" |
| module.exports = { |
| plugins: |
| process.env.NODE_ENV === 'production' |
| ? [ |
| 'postcss-flexbugs-fixes', |
| [ |
| 'postcss-preset-env', |
| { |
| autoprefixer: { |
| flexbox: 'no-2009', |
| }, |
| stage: 3, |
| features: { |
| 'custom-properties': false, |
| }, |
| }, |
| ], |
| ] |
| : [ |
| // No transformations in development |
| ], |
| } |
| ``` |
| |
| > **Good to know**: Next.js also allows the file to be named `.postcssrc.js`. |
| |
| Do **not use `require()`** to import the PostCSS Plugins. Plugins must be provided as strings. |
| |
| > **Good to know**: If your `postcss.config.js` needs to support other non-Next.js tools in the same project, you must use the interoperable object-based format instead: |
| > |
| > ```js |
| > module.exports = { |
| > plugins: { |
| > 'postcss-flexbugs-fixes': {}, |
| > 'postcss-preset-env': { |
| > autoprefixer: { |
| > flexbox: 'no-2009', |
| > }, |
| > stage: 3, |
| > features: { |
| > 'custom-properties': false, |
| > }, |
| > }, |
| > }, |
| > } |
| > ``` |
| |
