# Dev

> Options that only affect the development server (`nitro dev`).

::note
All examples on this page assume the following import in `nitro.config.ts`:

```ts
import { defineConfig } from "nitro";
```
::

### `devServer`

- Default: `{ watch: [] }`{lang=ts}

Dev server options. You can use `watch` to make the dev server reload if any file changes in specified paths.

Supports `port`, `hostname`, `watch`, `runner`, `drain`, and `devtoolsJson` options.

```ts
export default defineConfig({
  devServer: {
    port: 3001,
    watch: ["./server/plugins"],
  },
});
```

By default, the dev server serves `/.well-known/appspecific/com.chrome.devtools.json` so Chrome DevTools can connect your project folder as an [automatic workspace](https://chromium.googlesource.com/devtools/devtools-frontend/+/main/docs/ecosystem/automatic_workspace_folders.md) and save edits back to source files. The workspace UUID is persisted in `buildDir`. Set `devServer.devtoolsJson: false` to disable it.

By default, a reload shuts the previous dev worker down first: new requests wait for it, and requests, streamed responses and WebSockets still open after 5 seconds are cut. Set `devServer.drain: true` to let it finish them while new requests go to the new worker. It is shut down once they settle, or after 60 seconds (`drain: { timeout: 600_000 }` for a custom limit, `Infinity` for none).

### `watchOptions`

Watch options for development mode. See [chokidar](https://github.com/paulmillr/chokidar) for more information.

```ts
export default defineConfig({
  watchOptions: {
    ignored: ["**/node_modules/**", "**/dist/**"],
  },
});
```

### `devProxy`

Proxy configuration for development server.

You can use this option to override development server routes and proxy-pass requests.

```ts
export default defineConfig({
  devProxy: {
    "/proxy/test": "http://localhost:3001",
    "/proxy/example": { target: "https://example.com", changeOrigin: true },
    "/proxy/socket/**": { target: "http://localhost:3002", ws: true },
  },
});
```

Routes match like other Nitro routes: `/proxy/test` only matches that exact path, use `/proxy/test/**` to also proxy sub-paths. Set `ws: true` to also proxy WebSocket upgrade requests.

See [httpxy](https://github.com/unjs/httpxy) for all available target options.

::note
When the dev server runs on Bun or Deno (e.g. `bun --bun nitro dev`), it listens with the runtime's native server. HTTP requests are then proxied with `proxyFetch` from httpxy, supporting `target`, `headers`, `auth`, `xfwd`, `changeOrigin`, `secure`, `ssl`, `agent`, `prependPath`, `ignorePath`, `proxyTimeout` and `followRedirects`. WebSockets are proxied with the [crossws](https://crossws.h3.dev) proxy, supporting `target`, `headers`, `auth`, `xfwd`, `prependPath` and `ignorePath` (the upstream `Host` header always matches the target). WebSocket upgrades to the dev worker of the `miniflare` runner (Cloudflare presets) are only supported on Node.js.
::