# Advanced Middleware

In the main tutorial you read how to add [Custom Middleware](../tutorial/middleware.md){.internal-link target=_blank} to your application.

And then you also read how to handle [CORS with the `CORSMiddleware`](../tutorial/cors.md){.internal-link target=_blank}.

In this section we'll see how to use other middlewares.

## Adding ASGI middlewares

# Advanced Security

## Additional Features

There are some extra features to handle security apart from the ones covered in the [Tutorial - User Guide: Security](../../tutorial/security/index.md){.internal-link target=_blank}.

!!! tip
    The next sections are **not necessarily "advanced"**.

    And it's possible that for your use case, the solution is in one of them.

## Read the Tutorial first

```

## Other middlewares

You can later read more about other middlewares in the [Advanced User Guide: Advanced Middleware](../advanced/middleware.md){.internal-link target=_blank}.

It can't handle nested models very well. So, if the JSON body in the request is a JSON object that has inner fields that in turn are nested JSON objects, it cannot be properly documented and validated.

!!! check "Inspired **FastAPI** to"

* Restarts
* Replication (the number of processes running)
* Memory
* Previous steps before starting

In these cases you can use `root_path` to configure your application.

The `root_path` is a mechanism provided by the ASGI specification (that FastAPI is built on, through Starlette).

The `root_path` is used to handle these specific cases.

And it's also used internally when mounting sub-applications.

## Proxy with a stripped path prefix

```

</div>

### Docs Structure

The documentation uses <a href="https://www.mkdocs.org/" class="external-link" target="_blank">MkDocs</a>.

And there are extra tools/scripts in place to handle translations in `./scripts/docs.py`.

!!! tip
    You don't need to see the code in `./scripts/docs.py`, you just use it in the command line.

All the documentation is in Markdown format in the directory `./docs/en/`.

```Python hl_lines="8-9"
{!> ../../../docs_src/response_model/tutorial003_03.py!}
```

This will also work because `RedirectResponse` is a subclass of `Response`, and FastAPI will automatically handle this simple case.

### Invalid Return Type Annotations

# OpenAPI

There are several utilities to handle OpenAPI.

Some of the options you could use as a TLS Termination Proxy are:

* Traefik (that can also handle certificate renewals)
* Caddy (that can also handle certificate renewals)
* Nginx
* HAProxy

## Let's Encrypt

Before Let's Encrypt, these **HTTPS certificates** were sold by trusted third parties.