## Conditional OpenAPI from settings and env vars

You can easily use the same Pydantic settings to configure your generated OpenAPI and the docs UIs.

For example:

{* ../../docs_src/conditional_openapi/tutorial001.py hl[6,11] *}

Here we declare the setting `openapi_url` with the same default of `"/openapi.json"`.

# Sub Applications - Mounts

If you need to have two independent FastAPI applications, with their own independent OpenAPI and their own docs UIs, you can have a main app and "mount" one (or more) sub-application(s).

## Mounting a **FastAPI** application

"Mounting" means adding a completely "independent" application in a specific path, that then takes care of handling everything under that path, with the _path operations_ declared in that sub-application.

You can customize several metadata configurations in your **FastAPI** application.

## Metadata for API

You can set the following fields that are used in the OpenAPI specification and the automatic API docs UIs:

| Parameter | Type | Description |
|------------|------|-------------|
| `title` | `str` | The title of the API. |

* Diese Schemas werden Teil des generierten OpenAPI-Schemas und werden von den <abbr title="User Interface – Benutzeroberfläche">UIs</abbr> der automatischen Dokumentation verwendet.

## Automatische Dokumentation

Die JSON-Schemas Ihrer Modelle werden Teil ihrer OpenAPI-generierten Schemas und werden in der interaktiven API Dokumentation angezeigt:

* Esses esquemas farão parte do esquema OpenAPI, e utilizados nas <abbr title="User Interfaces">UIs</abbr> de documentação automática.

## Documentação automática

Os esquemas JSON dos seus modelos farão parte do esquema OpenAPI gerado para sua aplicação, e aparecerão na documentação interativa da API:

* Those schemas will be part of the generated OpenAPI schema, and used by the automatic documentation <abbr title="User Interfaces">UIs</abbr>.

## Automatic docs

The JSON Schemas of your models will be part of your OpenAPI generated schema, and will be shown in the interactive API docs:

<img src="/img/tutorial/body/image01.png">

* Remove obsolete vote link. PR [#1289](https://github.com/tiangolo/fastapi/pull/1289) by [@donhui](https://github.com/donhui).
* Allow disabling docs UIs by just disabling OpenAPI with `openapi_url=None`. New example in docs: [Advanced: Conditional OpenAPI](https://fastapi.tiangolo.com/advanced/conditional-openapi/). PR [#1421](https://github.com/tiangolo/fastapi/pull/1421).