{!../../../docs_src/custom_response/tutorial009.py!}
```
+## Default response class
+
+When creating a **FastAPI** class instance or an `APIRouter` you can specify which response class to use by default.
+
+The parameter that defines this is `default_response_class`.
+
+In the example below, **FastAPI** will use `ORJSONResponse` by default, in all *path operations*, instead of `JSONResponse`.
+
+```Python hl_lines="2 4"
+{!../../../docs_src/custom_response/tutorial010.py!}
+```
+
+!!! tip
+ You can still override `response_class` in *path operations* as before.
+
## Additional documentation
You can also declare the media type and many other details in OpenAPI using `responses`: [Additional Responses in OpenAPI](additional-responses.md){.internal-link target=_blank}.
--- /dev/null
+from fastapi import FastAPI
+from fastapi.responses import ORJSONResponse
+
+app = FastAPI(default_response_class=ORJSONResponse)
+
+
+@app.get("/items/")
+async def read_items():
+ return [{"item_id": "Foo"}]