// Perform customizations to webpack dev middleware config
// Important: return the modified config
return config
},
}
```
> The `webpack` function is executed twice, once for the server and once for the client. This allows you to distinguish between client and server configuration using the `isServer` property.
The second argument to the `webpack` function is an object with the following properties:
-`buildId`: `String` - The build id, used as a unique identifier between builds
-`dev`: `Boolean` - Indicates if the compilation will be done in development
-`isServer`: `Boolean` - It's `true` for server-side compilation, and `false` for client-side compilation
-`defaultLoaders`: `Object` - Default loaders used internally by Next.js: