For production you would use `fastapi run` instead. 🚀

Internally, **FastAPI CLI** uses <a href="https://www.uvicorn.org" class="external-link" target="_blank">Uvicorn</a>, a high-performance, production-ready, ASGI server. 😎

## `fastapi dev`

When you run `fastapi dev`, it will run on development mode.

**Source Code**: <a href="https://github.com/tiangolo/fastapi" target="_blank">https://github.com/tiangolo/fastapi</a>

---

FastAPI is a modern, fast (high-performance), web framework for building APIs with Python based on standard Python type hints.

The key features are:

* **Fast**: Very high performance, on par with **NodeJS** and **Go** (thanks to Starlette and Pydantic). [One of the fastest Python frameworks available](#performance).

INHERIT: ../en/mkdocs.maybe-insiders.yml
site_name: FastAPI
site_description: FastAPI framework, high performance, easy to learn, fast to code, ready for production
site_url: https://fastapi.tiangolo.com/
theme:
  name: material
  custom_dir: ../en/overrides
  palette:
  - media: '(prefers-color-scheme: light)'
    scheme: default
    primary: teal
    accent: amber
    toggle:
      icon: material/lightbulb
      name: Switch to dark mode

**Source Code**: <a href="https://github.com/tiangolo/fastapi" target="_blank">https://github.com/tiangolo/fastapi</a>

---

FastAPI is a modern, fast (high-performance), web framework for building APIs with Python based on standard Python type hints.

The key features are:

* **Fast**: Very high performance, on par with **NodeJS** and **Go** (thanks to Starlette and Pydantic). [One of the fastest Python frameworks available](#performance).

    But `open()` doesn't use `async` and `await`.

    So, we declare the event handler function with standard `def` instead of `async def`.

### `startup` and `shutdown` together

There's a high chance that the logic for your *startup* and *shutdown* is connected, you might want to start something and then finish it, acquire a resource and then release it, etc.

<div class="termy">

```console
$ pip install "uvicorn[standard]" gunicorn

---> 100%
```

</div>

That will install both Uvicorn with the `standard` extra packages (to get high performance) and Gunicorn.

## Run Gunicorn with Uvicorn Workers

Then you can run Gunicorn with:

<div class="termy">

```console

    * This solves a vulnerability that could allow denial of service attacks by using many small multipart fields/files (parts), consuming high CPU and memory.
    * Only applications using forms (e.g. file uploads) could be affected.
    * For most cases, upgrading won't have any breaking changes.

## 0.91.0

### Upgrades

</style>

<p align="center">
  <a href="https://fastapi.tiangolo.com"><img src="https://fastapi.tiangolo.com/img/logo-margin/logo-teal.png" alt="FastAPI"></a>
</p>
<p align="center">
    FastAPI framework, high performance, easy to learn, fast to code, ready for production
</p>
<p align="center">
<a href="https://travis-ci.com/tiangolo/fastapi" target="_blank">

Previous versions of FastAPI (before <abbr title="before 2023-03">0.95.0</abbr>) required you to use `Query` as the default value of your parameter, instead of putting it in `Annotated`, there's a high chance that you will see code using it around, so I'll explain it to you.

!!! tip
    For new code and whenever possible, use `Annotated` as explained above. There are multiple advantages (explained below) and no disadvantages. 🍰

* <a href="https://github.com/tiangolo/uvicorn-gunicorn-fastapi-docker" class="external-link" target="_blank">tiangolo/uvicorn-gunicorn-fastapi</a>.

!!! warning
    There's a high chance that you **don't** need this base image or any other similar one, and would be better off by building the image from scratch as [described above in: Build a Docker Image for FastAPI](#build-a-docker-image-for-fastapi).