> For AI agents: the complete documentation index is available at /llms.txt, the full documentation bundle is available at /llms-full.txt.

# server.strictPort

- **Type:** `boolean`
- **Default:** `false`

When a port is occupied, Rsbuild will automatically increment the port number until an available port is found.

Set `strictPort` to `true` and Rsbuild will throw an exception when the port is occupied.

## Example

### Basic usage

Enable strict port mode to ensure the dev server fails if the specified port is occupied:

```ts title="rsbuild.config.ts"
export default {
  server: {
    strictPort: true,
  },
};
```

### Use with specific port

When you need to ensure your application runs on a specific port:

```ts title="rsbuild.config.ts"
export default {
  server: {
    port: 3333,
    strictPort: true,
  },
};
```

With this configuration, if port 3333 is already in use, Rsbuild will throw an error instead of automatically using port 3334.