# CORS (Cross-Origin Resource Sharing)

<a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS" class="external-link" target="_blank">CORS or "Cross-Origin Resource Sharing"</a> refers to the situations when a frontend running in a browser has JavaScript code that communicates with a backend, and the backend is in a different "origin" than the frontend.

## Origin

        return True
    origin = get_origin(annotation)
    if origin is Union or origin is UnionType:
        for arg in get_args(annotation):
            if lenient_issubclass(arg, UploadFile):
                return True
    return False


def is_bytes_sequence_annotation(annotation: Any) -> bool:
    origin = get_origin(annotation)
    if origin is Union or origin is UnionType:
        at_least_one = False

{!../../../docs_src/middleware/tutorial001.py!}
```

## 🎏 🛠️

👆 💪 ⏪ ✍ 🌖 🔃 🎏 🛠️ [🏧 👩‍💻 🦮: 🏧 🛠️](../advanced/middleware.md){.internal-link target=_blank}.

from starlette.requests import HTTPConnection, Request
from starlette.responses import Response
from starlette.websockets import WebSocket
from typing_extensions import Annotated, get_args, get_origin

multipart_not_installed_error = (
    'Form data requires "python-multipart" to be installed. \n'
    'You can install "python-multipart" with: \n\n'
    "pip install python-multipart\n"
)

```

Bu satır, yerel makinenizde uygulamanızın çalıştığı bağlantıyı gösterir.

### Kontrol Edelim

Tarayıcınızı açıp <a href="http://127.0.0.1:8000" class="external-link" target="_blank">http://127.0.0.1:8000</a> bağlantısına gidin.

Şu şekilde bir JSON yanıtı ile karşılaşacağız:

```JSON
{"message": "Hello World"}
```

### Etkileşimli API Dokümantasyonu