fastify/docs/Middleware.md

Fast and low overhead web framework, for Node.js

<h1 align="center">Fastify</h1>

## Middleware

Starting with Fastify v3.0.0, middleware is not supported out of the box and requires an external plugin such as [`fastify-express`](https://github.com/fastify/fastify-express) or [`middie`](https://github.com/fastify/middie).


An example of registering the [`fastify-express`](https://github.com/fastify/fastify-express) plugin to `use` Express middleware:

```js
await fastify.register(require('fastify-express'))
fastify.use(require('cors')())
fastify.use(require('dns-prefetch-control')())
fastify.use(require('frameguard')())
fastify.use(require('hsts')())
fastify.use(require('ienoopen')())
fastify.use(require('x-xss-protection')())
```

You can also use [`middie`](https://github.com/fastify/middie), which provides support for simple Express-style middleware but with improved performance:

```js
await fastify.register(require('middie'))
fastify.use(require('cors')())
```

Remember that middleware can be encapsulated; this means that you can decide where your middleware should run by using `register` as explained in the [plugins guide](Plugins-Guide.md).

Fastify middleware do not expose the `send` method or other methods specific to the Fastify [Reply](Reply.md#reply) instance. This is because Fastify wraps the incoming `req` and `res` Node instances using the [Request](Request.md#request) and [Reply](Reply.md#reply) objects internally, but this is done after the middleware phase. If you need to create middleware, you have to use the Node `req` and `res` instances. Otherwise, you can use the `preHandler` hook that already has the [Request](Request.md#request) and [Reply](Reply.md#reply) Fastify instances. For more information, see [Hooks](Hooks.md#hooks).

<a name="restrict-usage"></a>
#### Restrict middleware execution to a certain path(s)
If you need to run a middleware only under certain path(s), just pass the path as first parameter to `use` and you are done!

*Note that this does not support routes with parameters, (eg: `/user/:id/comments`) and wildcards are not supported in multiple paths.*

```js
const path = require('path')
const serveStatic = require('serve-static')

// Single path
fastify.use('/css', serveStatic(path.join(__dirname, '/assets')))

// Wildcard path
fastify.use('/css/(.*)', serveStatic(path.join(__dirname, '/assets')))

// Multiple paths
fastify.use(['/css', '/js'], serveStatic(path.join(__dirname, '/assets')))
```

### Alternatives

Fastify offers some alternatives to the most commonly used middleware, such as [`fastify-helmet`](https://github.com/fastify/fastify-helmet) in case of [`helmet`](https://github.com/helmetjs/helmet), [`fastify-cors`](https://github.com/fastify/fastify-cors) for [`cors`](https://github.com/expressjs/cors) and [`fastify-static`](https://github.com/fastify/fastify-static) for [`serve-static`](https://github.com/expressjs/serve-static).