<a href="https://github.com/scalar/scalar/?utm_source=fastapi&utm_medium=website&utm_campaign=main-badge" target="_blank" title="Scalar: Beautiful Open-Source API References from Swagger/OpenAPI files"><img src="https://fastapi.tiangolo.com/img/sponsors/scalar.svg"></a>

### Based on open standards

* <a href="https://github.com/OAI/OpenAPI-Specification" class="external-link" target="_blank"><strong>OpenAPI</strong></a> for API creation, including declarations of <abbr title="also known as: endpoints, routes">path</abbr> <abbr title="also known as HTTP methods, as POST, GET, PUT, DELETE">operations</abbr>, parameters, body requests, security, etc.

## An app with callbacks

Let's see all this with an example.

Imagine you develop an app that allows creating invoices.

These invoices will have an `id`, `title` (optional), `customer`, and `total`.

The user of your API (an external developer) will create an invoice in your API with a POST request.

Then your API will (let's imagine):

A **container** is run from a **container image**.

A container image is a **static** version of all the files, environment variables, and the default command/program that should be present in a container. **Static** here means that the container **image** is not running, it's not being executed, it's only the packaged files and metadata.

It will show a JSON starting with something like:

```JSON
{
    "openapi": "3.1.0",
    "info": {
        "title": "FastAPI",
        "version": "0.1.0"
    },
    "paths": {
        "/items/": {
            "get": {
                "responses": {
                    "200": {

## ASGI Servers

Let's go a little deeper into the details.

FastAPI uses a standard for building Python web frameworks and servers called <abbr title="Asynchronous Server Gateway Interface">ASGI</abbr>. FastAPI is an ASGI web framework.

<!-- sponsors -->

{% if sponsors %}
{% for sponsor in sponsors.gold -%}
<a href="{{ sponsor.url }}" target="_blank" title="{{ sponsor.title }}"><img src="{{ sponsor.img }}" style="border-radius:15px"></a>
{% endfor -%}
{%- for sponsor in sponsors.silver -%}
<a href="{{ sponsor.url }}" target="_blank" title="{{ sponsor.title }}"><img src="{{ sponsor.img }}" style="border-radius:15px"></a>
{% endfor %}
{% endif %}

<!-- /sponsors -->

build --define tsl_protobuf_header_only=true

build --define=use_fast_cpp_protos=true
build --define=allow_oversize_protos=true

build --spawn_strategy=standalone
build -c opt

# Make Bazel print out all options from rc files.
build --announce_rc

# TODO(mihaimaruseac): Document this option or remove if no longer needed
build --define=grpc_no_ares=true

# See https://github.com/bazelbuild/bazel/issues/7362 for information on what

- Select a Java 11 VM as "Gradle JVM"
- In the "File already exists" dialogue, choose "Yes" to overwrite
- In the "Open Project" dialogue, choose "Delete Existing Project and Import"
- Revert the Git changes to files in the `.idea` folder

NOTE: Due to the project size, the very first import can take a while and IntelliJ might become unresponsive for several seconds during this period.

    * The same new ID generation applies to response models.
    * This also changes the generated title for those models.
    * Only composite bodies and response models are affected because those are generated dynamically, they don't have a module (a Python file).
    * This also adds the possibility of using `.include_router()` with the same `APIRouter` *multiple*  times, with different prefixes, e.g. `/api/v2` and `/api/latest`, and it will now work correctly.