react-code-dataset / next.js /docs /02-pages /04-api-reference /04-config /01-next-config-js /runtime-configuration.mdx
| --- | |
| title: Runtime Config | |
| description: Add client and server runtime configuration to your Next.js app. | |
| --- | |
| **Warning:** | |
| - **This feature is deprecated.** We recommend using [environment variables](/docs/pages/guides/environment-variables) instead, which also can support reading runtime values. | |
| - You can run code on server startup using the [`register` function](/docs/app/guides/instrumentation). | |
| - This feature does not work with [Automatic Static Optimization](/docs/pages/building-your-application/rendering/automatic-static-optimization), [Output File Tracing](/docs/pages/api-reference/config/next-config-js/output#automatically-copying-traced-files), or [React Server Components](/docs/app/getting-started/server-and-client-components). | |
| To add runtime configuration to your app, open `next.config.js` and add the `publicRuntimeConfig` and `serverRuntimeConfig` configs: | |
| ```js filename="next.config.js" | |
| module.exports = { | |
| serverRuntimeConfig: { | |
| // Will only be available on the server side | |
| mySecret: 'secret', | |
| secondSecret: process.env.SECOND_SECRET, // Pass through env variables | |
| }, | |
| publicRuntimeConfig: { | |
| // Will be available on both server and client | |
| staticFolder: '/static', | |
| }, | |
| } | |
| ``` | |
| Place any server-only runtime config under `serverRuntimeConfig`. | |
| Anything accessible to both client and server-side code should be under `publicRuntimeConfig`. | |
| A page that relies on `publicRuntimeConfig` **must** use `getInitialProps` or `getServerSideProps` or your application must have a [Custom App](/docs/pages/building-your-application/routing/custom-app) with `getInitialProps` to opt-out of [Automatic Static Optimization](/docs/pages/building-your-application/rendering/automatic-static-optimization). Runtime configuration won't be available to any page (or component in a page) without being server-side rendered. | |
| To get access to the runtime configs in your app use `next/config`, like so: | |
| ```jsx | |
| import getConfig from 'next/config' | |
| import Image from 'next/image' | |
| // Only holds serverRuntimeConfig and publicRuntimeConfig | |
| const { serverRuntimeConfig, publicRuntimeConfig } = getConfig() | |
| // Will only be available on the server-side | |
| console.log(serverRuntimeConfig.mySecret) | |
| // Will be available on both server-side and client-side | |
| console.log(publicRuntimeConfig.staticFolder) | |
| function MyImage() { | |
| return ( | |
| <div> | |
| <Image | |
| src={`${publicRuntimeConfig.staticFolder}/logo.png`} | |
| alt="logo" | |
| layout="fill" | |
| /> | |
| </div> | |
| ) | |
| } | |
| export default MyImage | |
| ``` | |