Configuration

This file will often be mentioned in the documentation, for example to add custom scripts, register modules or change rendering modes.

::read-more{to="/docs/4.x/api/configuration/nuxt-config"}
Every option is described in the **Configuration Reference**.
::

::note
You don't have to use TypeScript to build an application with Nuxt. However, it is strongly recommended to use the `.ts` extension for the `nuxt.config` file. This way you can benefit from hints in your IDE to avoid typos and mistakes while editing your configuration.
::

### Environment Overrides

You can configure fully typed, per-environment overrides in your nuxt.config

```ts twoslash [nuxt.config.ts]
export default defineNuxtConfig({
  $production: {
    routeRules: {
      '/**': { isr: true },
    },
  },
  $development: {
    //
  },
  $env: {
    staging: {
      //
    },
  },
})

```ini [.env]
# This will override the value of apiSecret
NUXT_API_SECRET=api_secret_token

:read-more{to="/docs/4.x/guide/going-further/runtime-config"}

## App Configuration

The `app.config.ts` file, located in the source directory (by default `app/`), is used to expose public variables that can be determined at build time. Contrary to the `runtimeConfig` option, these cannot be overridden using environment variables.

A minimal configuration file exports the `defineAppConfig` function containing an object with your configuration. The `defineAppConfig` helper is globally available without import.

```ts [app/app.config.ts]
export default defineAppConfig({
  title: 'Hello Nuxt',
  theme: {
    dark: true,
    colors: {
      primary: '#ff0000',
    },
  },
})

:read-more{to="/docs/4.x/directory-structure/app/app-config"}

## `runtimeConfig` vs. `app.config`

As stated above, `runtimeConfig` and `app.config` are both used to expose variables to the rest of your application. To determine whether you should use one or the other, here are some guidelines:

- `runtimeConfig`: Private or public tokens that need to be specified after build using environment variables.
- `app.config`: Public tokens that are determined at build time, website configuration such as theme variant, title and any project config that are not sensitive.

| Feature                   | `runtimeConfig` | `app.config` |
|---------------------------|-----------------|--------------|
| Client-side               | Hydrated        | Bundled      |
| Environment variables     | ✅ Yes           | ❌ No         |
| Reactive                  | ✅ Yes           | ✅ Yes        |
| Types support             | ✅ Partial       | ✅ Yes        |
| Configuration per request | ❌ No            | ✅ Yes        |
| Hot module replacement    | ❌ No            | ✅ Yes        |
| Non-primitive JS types    | ❌ No            | ✅ Yes        |

## External Configuration Files

Nuxt uses [`nuxt.config.ts`](/docs/4.x/directory-structure/nuxt-config) file as the single source of truth for configurations and skips reading external configuration files. During the course of building your project, you may have a need to configure those. The following table highlights common configurations and, where applicable, how they can be configured with Nuxt.

| Name                              | Config File             | How To Configure                                                          |
|-----------------------------------|-------------------------|---------------------------------------------------------------------------|
| [Nitro](https://nitro.build)      | ~~`nitro.config.ts`~~   | Use [`nitro`](/docs/4.x/api/nuxt-config#nitro) key in `nuxt.config`       |
| [PostCSS](https://postcss.org)    | ~~`postcss.config.js`~~ | Use [`postcss`](/docs/4.x/api/nuxt-config#postcss) key in `nuxt.config`   |
| [Vite](https://vite.dev)          | ~~`vite.config.ts`~~    | Use [`vite`](/docs/4.x/api/nuxt-config#vite) key in `nuxt.config`         |
| [webpack](https://webpack.js.org) | ~~`webpack.config.ts`~~ | Use [`webpack`](/docs/4.x/api/nuxt-config#webpack-1) key in `nuxt.config` |

Here is a list of other common config files:

| Name                                         | Config File           | How To Configure                                                              |
|----------------------------------------------|-----------------------|-------------------------------------------------------------------------------|
| [TypeScript](https://www.typescriptlang.org) | `tsconfig.json`       | [More Info](/docs/4.x/directory-structure/tsconfig)                           |
| [ESLint](https://eslint.org)                 | `eslint.config.js`    | [More Info](https://eslint.org/docs/latest/use/configure/configuration-files) |
| [Prettier](https://prettier.io)              | `prettier.config.js`  | [More Info](https://prettier.io/docs/configuration.html)                      |
| [Stylelint](https://stylelint.io)            | `stylelint.config.js` | [More Info](https://stylelint.io/user-guide/configure/)                       |
| [TailwindCSS](https://tailwindcss.com)       | `tailwind.config.js`  | [More Info](https://tailwindcss.nuxtjs.org/tailwindcss/configuration/)        |
| [Vitest](https://vitest.dev)                 | `vitest.config.ts`    | [More Info](https://vitest.dev/config/)                                       |

## Vue Configuration

### With Vite

If you need to pass options to `@vitejs/plugin-vue` or `@vitejs/plugin-vue-jsx`, you can do this in your `nuxt.config` file.

- `vite.vue` for `@vitejs/plugin-vue`. Check [available options](https://github.com/vitejs/vite-plugin-vue/tree/main/packages/plugin-vue).
- `vite.vueJsx` for `@vitejs/plugin-vue-jsx`. Check [available options](https://github.com/vitejs/vite-plugin-vue/tree/main/packages/plugin-vue-jsx).

```ts twoslash [nuxt.config.ts]
export default defineNuxtConfig({
  vite: {
    vue: {
      customElement: true,
    },
    vueJsx: {
      mergeProps: true,
    },
  },
})

:read-more{to="/docs/4.x/api/configuration/nuxt-config#loaders"}

### Enabling Experimental Vue Features

You may need to enable experimental features in Vue, such as `propsDestructure`. Nuxt provides an easy way to do that in `nuxt.config.ts`, no matter which builder you are using:

```ts twoslash [nuxt.config.ts]
export default defineNuxtConfig({
  vue: {
    propsDestructure: true,
  },
})