---
title: 'Invalid `next.config.js`'
---

## Why this error occurred

In your `next.config.js` file, you passed invalid options that either are the incorrect type or an unknown field. This warning is shown to help catch typos, deprecated or updated options.

## Possible ways to fix it

You can use the `NextConfig` type to help ensure your config is correct.

```js filename="next.config.js"
/**
 * @type {import('next').NextConfig}
 */
const nextConfig = {
  /* config options here */
}

module.exports = nextConfig
```

Alternatively, you can use `next.config.ts` for better type safety and auto-completion:

```ts filename="next.config.ts"
import type { NextConfig } from 'next'

const nextConfig: NextConfig = {
  /* config options here */
}

export default nextConfig
```

### Deprecated or updated options

Some configuration options have been removed or updated in recent versions of Next.js. For example:

- `eslint` configuration option has been removed from `next.config`. Remove the `eslint` option and use the ESLint CLI instead. See the [ESLint](/docs/app/api-reference/config/eslint) documentation.
- `experimental.turbo` configuration has moved to a top-level `turbopack` configuration. See the [`turbopack` option](/docs/app/api-reference/config/next-config-js/turbopack) documentation.

See the [`next.config.js` docs](/docs/app/api-reference/config/next-config-js) for a list of all available and legacy options.

## Useful links

- [`next.config.js`](/docs/pages/api-reference/config/next-config-js)
