---
description: Add client and server runtime configuration to your Next.js app.
---
# Runtime Configuration
> Generally you'll want to use [build-time environment variables](/docs/api-reference/next.config.js/environment-variables.md) to provide your configuration. The reason for this is that runtime configuration adds rendering / initialization overhead and is incompatible with [Automatic Static Optimization](/docs/advanced-features/automatic-static-optimization.md).
> Runtime configuration is not available when using the [`serverless` target](/docs/api-reference/next.config.js/build-target.md#serverless-target).
To add runtime configuration to your app open `next.config.js` and add the `publicRuntimeConfig` and `serverRuntimeConfig` configs:
```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` to opt-out of [Automatic Static Optimization](/docs/advanced-features/automatic-static-optimization.md). Runtime configuration won't be available to any page (or component in a page) without `getInitialProps`.
To get access to the runtime configs in your app use `next/config`, like so:
```jsx
import getConfig from 'next/config'
// 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 (
)
}
export default MyImage
```
## Related
