![ReDoc](https://fastapi.tiangolo.com/img/index/index-02-redoc-simple.png)

### OpenAPI

**FastAPI** generates a "schema" with all your API using the **OpenAPI** standard for defining APIs.

#### "Schema"

A "schema" is a definition or description of something. Not the code that implements it, but just an abstract description.

            "description": "Production environment"
        }
    ],
    "paths": {
            // More stuff here
    }
}
```

!!! tip
    Notice the auto-generated server with a `url` value of `/api/v1`, taken from the `root_path`.

In the docs UI at <a href="http://127.0.0.1:9999/api/v1/docs" class="external-link" target="_blank">http://127.0.0.1:9999/api/v1/docs</a> it would look like:

* Fix OpenAPI/JSON Schema generation for two functions with the same name (in different modules) with the same composite bodies.
    * Composite bodies' IDs are now based on path, not only on route name, as the auto-generated name uses the function names, that can be duplicated in different modules.
    * The same new ID generation applies to response models.
    * This also changes the generated title for those models.

    "jinja2 >=2.11.2",
    # For forms and file uploads
    "python-multipart >=0.0.7",
    # For Starlette's SessionMiddleware, not commonly used with FastAPI
    "itsdangerous >=1.1.0",
    # For Starlette's schema generation, would not be used with FastAPI
    "pyyaml >=5.3.1",
    # For UJSONResponse
    "ujson >=4.0.1,!=4.0.2,!=4.1.0,!=4.2.0,!=4.3.0,!=5.0.0,!=5.1.0",
    # For ORJSONResponse
    "orjson >=3.2.1",

  - reference/encoders.md
  - reference/staticfiles.md
  - reference/templating.md
  - reference/testclient.md
- fastapi-people.md
- Resources:
  - resources/index.md
  - project-generation.md
  - external-links.md
  - newsletter.md
- About:
  - about/index.md
  - alternatives.md
  - history-design-future.md
  - benchmarks.md
- Help:
  - help/index.md
  - help-fastapi.md

* Designed around these standards, after a meticulous study. Instead of an afterthought layer on top.
* This also allows using automatic **client code generation** in many languages.

### Automatic docs

Interactive API documentation and exploration web user interfaces. As the framework is based on OpenAPI, there are multiple options, 2 included by default.

<a href="https://bump.sh/fastapi?utm_source=fastapi&utm_medium=referral&utm_campaign=sponsor" target="_blank" title="Automate FastAPI documentation generation with Bump.sh"><img src="https://fastapi.tiangolo.com/img/sponsors/bump-sh.svg"></a>
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                It will be included in the generated OpenAPI (e.g. visible at `/docs`).
                """
            ),
        ] = None,
        description: Annotated[
            Optional[str],
            Doc(
                """
                Security scheme description.

                It will be included in the generated OpenAPI (e.g. visible at `/docs`).
                """
            ),

9. Install the package dependencies in the generated `requirements.txt` file.

10. Copy the `app` directory to the `/code` directory.

11. Use the `fastapi run` command to run your app.

!!! tip
    Click the bubble numbers to see what each line does.

A **Docker stage** is a part of a `Dockerfile` that works as a **temporary container image** that is only used to generate some files to be used later.

* Convert from and to JSON automatically.
* Document everything with OpenAPI, that can be used by:
    * Interactive documentation systems.
    * Automatic client code generation systems, for many languages.
* Provide 2 interactive documentation web interfaces directly.

---

We just scratched the surface, but you already get the idea of how it all works.

Try changing the line with: