Nuxt/docs/content/3.server/3.middleware.md

# Server Middleware

Nuxt will automatically read in any files in the `~/server/middleware` to create server middleware for your project.

These files will be run on every request, unlike [API routes](./api) that are mapped to their own routes. This is typically so you can add a common header to all responses, log responses or modify the incoming request object for use later on in the request chain.

Each file should export a default function that will handle a request.

```js
export default async (req, res) => {
  req.someValue = true
}
```

There is nothing different about the `req`/`res` objects, so typing them is straightforward.

```ts
import type { IncomingMessage, ServerResponse } from 'http'

export default async (req: IncomingMessage, res: ServerResponse) => {
  req.someValue = true
}
```