# updateAppConfig
> Update the App Config at runtime.
Updates the [`app.config`](/docs/4.x/directory-structure/app/app-config) using deep assignment. Existing (nested) properties will be preserved.
## Usage
```js
import { updateAppConfig, useAppConfig } from '#imports'
const appConfig = useAppConfig() // { foo: 'bar' }
const newAppConfig = { foo: 'baz' }
updateAppConfig(newAppConfig)
console.log(appConfig) // { foo: 'baz' }
```
---
- [Source](https://github.com/nuxt/nuxt/blob/main/packages/nuxt/src/app/config.ts)