diff --git a/Pipfile b/Pipfile
index c7cdb944e0ddc..f59b751a907d8 100644
--- a/Pipfile
+++ b/Pipfile
@@ -29,6 +29,7 @@ starlette = "==0.12.8"
 pydantic = "==0.32.2"
 databases = {extras = ["sqlite"],version = "*"}
 hypercorn = "*"
+orjson = "*"
 
 [requires]
 python_version = "3.6"
diff --git a/fastapi/applications.py b/fastapi/applications.py
index 7836801415e9b..28cbd319b79e9 100644
--- a/fastapi/applications.py
+++ b/fastapi/applications.py
@@ -33,11 +33,13 @@ def __init__(
         version: str = "0.1.0",
         openapi_url: Optional[str] = "/openapi.json",
         openapi_prefix: str = "",
+        default_response_class: Type[Response] = JSONResponse,
         docs_url: Optional[str] = "/docs",
         redoc_url: Optional[str] = "/redoc",
         swagger_ui_oauth2_redirect_url: Optional[str] = "/docs/oauth2-redirect",
         **extra: Dict[str, Any],
     ) -> None:
+        self.default_response_class = default_response_class
         self._debug = debug
         self.router: routing.APIRouter = routing.APIRouter(
             routes, dependency_overrides_provider=self
@@ -144,7 +146,7 @@ def add_api_route(
         response_model_by_alias: bool = True,
         response_model_skip_defaults: bool = False,
         include_in_schema: bool = True,
-        response_class: Type[Response] = JSONResponse,
+        response_class: Type[Response] = None,
         name: str = None,
     ) -> None:
         self.router.add_api_route(
@@ -166,7 +168,7 @@ def add_api_route(
             response_model_by_alias=response_model_by_alias,
             response_model_skip_defaults=response_model_skip_defaults,
             include_in_schema=include_in_schema,
-            response_class=response_class,
+            response_class=response_class or self.default_response_class,
             name=name,
         )
 
@@ -190,7 +192,7 @@ def api_route(
         response_model_by_alias: bool = True,
         response_model_skip_defaults: bool = False,
         include_in_schema: bool = True,
-        response_class: Type[Response] = JSONResponse,
+        response_class: Type[Response] = None,
         name: str = None,
     ) -> Callable:
         def decorator(func: Callable) -> Callable:
@@ -213,7 +215,7 @@ def decorator(func: Callable) -> Callable:
                 response_model_by_alias=response_model_by_alias,
                 response_model_skip_defaults=response_model_skip_defaults,
                 include_in_schema=include_in_schema,
-                response_class=response_class,
+                response_class=response_class or self.default_response_class,
                 name=name,
             )
             return func
@@ -240,6 +242,7 @@ def include_router(
         tags: List[str] = None,
         dependencies: Sequence[Depends] = None,
         responses: Dict[Union[int, str], Dict[str, Any]] = None,
+        default_response_class: Optional[Type[Response]] = None,
     ) -> None:
         self.router.include_router(
             router,
@@ -247,6 +250,8 @@ def include_router(
             tags=tags,
             dependencies=dependencies,
             responses=responses or {},
+            default_response_class=default_response_class
+            or self.default_response_class,
         )
 
     def get(
@@ -268,7 +273,7 @@ def get(
         response_model_by_alias: bool = True,
         response_model_skip_defaults: bool = False,
         include_in_schema: bool = True,
-        response_class: Type[Response] = JSONResponse,
+        response_class: Type[Response] = None,
         name: str = None,
     ) -> Callable:
         return self.router.get(
@@ -288,7 +293,7 @@ def get(
             response_model_by_alias=response_model_by_alias,
             response_model_skip_defaults=response_model_skip_defaults,
             include_in_schema=include_in_schema,
-            response_class=response_class,
+            response_class=response_class or self.default_response_class,
             name=name,
         )
 
@@ -311,7 +316,7 @@ def put(
         response_model_by_alias: bool = True,
         response_model_skip_defaults: bool = False,
         include_in_schema: bool = True,
-        response_class: Type[Response] = JSONResponse,
+        response_class: Type[Response] = None,
         name: str = None,
     ) -> Callable:
         return self.router.put(
@@ -331,7 +336,7 @@ def put(
             response_model_by_alias=response_model_by_alias,
             response_model_skip_defaults=response_model_skip_defaults,
             include_in_schema=include_in_schema,
-            response_class=response_class,
+            response_class=response_class or self.default_response_class,
             name=name,
         )
 
@@ -354,7 +359,7 @@ def post(
         response_model_by_alias: bool = True,
         response_model_skip_defaults: bool = False,
         include_in_schema: bool = True,
-        response_class: Type[Response] = JSONResponse,
+        response_class: Type[Response] = None,
         name: str = None,
     ) -> Callable:
         return self.router.post(
@@ -374,7 +379,7 @@ def post(
             response_model_by_alias=response_model_by_alias,
             response_model_skip_defaults=response_model_skip_defaults,
             include_in_schema=include_in_schema,
-            response_class=response_class,
+            response_class=response_class or self.default_response_class,
             name=name,
         )
 
@@ -397,7 +402,7 @@ def delete(
         response_model_by_alias: bool = True,
         response_model_skip_defaults: bool = False,
         include_in_schema: bool = True,
-        response_class: Type[Response] = JSONResponse,
+        response_class: Type[Response] = None,
         name: str = None,
     ) -> Callable:
         return self.router.delete(
@@ -417,7 +422,7 @@ def delete(
             operation_id=operation_id,
             response_model_skip_defaults=response_model_skip_defaults,
             include_in_schema=include_in_schema,
-            response_class=response_class,
+            response_class=response_class or self.default_response_class,
             name=name,
         )
 
@@ -440,7 +445,7 @@ def options(
         response_model_by_alias: bool = True,
         response_model_skip_defaults: bool = False,
         include_in_schema: bool = True,
-        response_class: Type[Response] = JSONResponse,
+        response_class: Type[Response] = None,
         name: str = None,
     ) -> Callable:
         return self.router.options(
@@ -460,7 +465,7 @@ def options(
             response_model_by_alias=response_model_by_alias,
             response_model_skip_defaults=response_model_skip_defaults,
             include_in_schema=include_in_schema,
-            response_class=response_class,
+            response_class=response_class or self.default_response_class,
             name=name,
         )
 
@@ -483,7 +488,7 @@ def head(
         response_model_by_alias: bool = True,
         response_model_skip_defaults: bool = False,
         include_in_schema: bool = True,
-        response_class: Type[Response] = JSONResponse,
+        response_class: Type[Response] = None,
         name: str = None,
     ) -> Callable:
         return self.router.head(
@@ -503,7 +508,7 @@ def head(
             response_model_by_alias=response_model_by_alias,
             response_model_skip_defaults=response_model_skip_defaults,
             include_in_schema=include_in_schema,
-            response_class=response_class,
+            response_class=response_class or self.default_response_class,
             name=name,
         )
 
@@ -526,7 +531,7 @@ def patch(
         response_model_by_alias: bool = True,
         response_model_skip_defaults: bool = False,
         include_in_schema: bool = True,
-        response_class: Type[Response] = JSONResponse,
+        response_class: Type[Response] = None,
         name: str = None,
     ) -> Callable:
         return self.router.patch(
@@ -546,7 +551,7 @@ def patch(
             response_model_by_alias=response_model_by_alias,
             response_model_skip_defaults=response_model_skip_defaults,
             include_in_schema=include_in_schema,
-            response_class=response_class,
+            response_class=response_class or self.default_response_class,
             name=name,
         )
 
@@ -569,7 +574,7 @@ def trace(
         response_model_by_alias: bool = True,
         response_model_skip_defaults: bool = False,
         include_in_schema: bool = True,
-        response_class: Type[Response] = JSONResponse,
+        response_class: Type[Response] = None,
         name: str = None,
     ) -> Callable:
         return self.router.trace(
@@ -589,6 +594,6 @@ def trace(
             response_model_by_alias=response_model_by_alias,
             response_model_skip_defaults=response_model_skip_defaults,
             include_in_schema=include_in_schema,
-            response_class=response_class,
+            response_class=response_class or self.default_response_class,
             name=name,
         )
diff --git a/fastapi/openapi/utils.py b/fastapi/openapi/utils.py
index 6c987a29fa915..d9ec7bd6e3c57 100644
--- a/fastapi/openapi/utils.py
+++ b/fastapi/openapi/utils.py
@@ -151,6 +151,10 @@ def get_openapi_path(
     security_schemes: Dict[str, Any] = {}
     definitions: Dict[str, Any] = {}
     assert route.methods is not None, "Methods must be a list"
+    assert (
+        route.response_class and route.response_class.media_type
+    ), "A response class with media_type is needed to generate OpenAPI"
+    route_response_media_type: str = route.response_class.media_type
     if route.include_in_schema:
         for method in route.methods:
             operation = get_openapi_operation_metadata(route=route, method=method)
@@ -185,7 +189,7 @@ def get_openapi_path(
                             field, model_name_map=model_name_map, ref_prefix=REF_PREFIX
                         )
                         response.setdefault("content", {}).setdefault(
-                            route.response_class.media_type, {}
+                            route_response_media_type, {}
                         )["schema"] = response_schema
                     status_text: Optional[str] = status_code_ranges.get(
                         str(additional_status_code).upper()
@@ -213,7 +217,7 @@ def get_openapi_path(
             ] = route.response_description
             operation.setdefault("responses", {}).setdefault(
                 status_code, {}
-            ).setdefault("content", {}).setdefault(route.response_class.media_type, {})[
+            ).setdefault("content", {}).setdefault(route_response_media_type, {})[
                 "schema"
             ] = response_schema
 
diff --git a/fastapi/routing.py b/fastapi/routing.py
index f7cec9e45a480..aeafd07187e81 100644
--- a/fastapi/routing.py
+++ b/fastapi/routing.py
@@ -200,7 +200,7 @@ def __init__(
         response_model_by_alias: bool = True,
         response_model_skip_defaults: bool = False,
         include_in_schema: bool = True,
-        response_class: Type[Response] = JSONResponse,
+        response_class: Optional[Type[Response]] = None,
         dependency_overrides_provider: Any = None,
     ) -> None:
         self.path = path
@@ -215,9 +215,6 @@ def __init__(
         )
         self.response_model = response_model
         if self.response_model:
-            assert lenient_issubclass(
-                response_class, JSONResponse
-            ), "To declare a type the response must be a JSON response"
             response_name = "Response_" + self.unique_id
             self.response_field: Optional[Field] = Field(
                 name=response_name,
@@ -299,7 +296,7 @@ def __init__(
                 dependant=self.dependant,
                 body_field=self.body_field,
                 status_code=self.status_code,
-                response_class=self.response_class,
+                response_class=self.response_class or JSONResponse,
                 response_field=self.secure_cloned_response_field,
                 response_model_include=self.response_model_include,
                 response_model_exclude=self.response_model_exclude,
@@ -346,7 +343,7 @@ def add_api_route(
         response_model_by_alias: bool = True,
         response_model_skip_defaults: bool = False,
         include_in_schema: bool = True,
-        response_class: Type[Response] = JSONResponse,
+        response_class: Type[Response] = None,
         name: str = None,
     ) -> None:
         route = self.route_class(
@@ -394,7 +391,7 @@ def api_route(
         response_model_by_alias: bool = True,
         response_model_skip_defaults: bool = False,
         include_in_schema: bool = True,
-        response_class: Type[Response] = JSONResponse,
+        response_class: Type[Response] = None,
         name: str = None,
     ) -> Callable:
         def decorator(func: Callable) -> Callable:
@@ -445,6 +442,7 @@ def include_router(
         tags: List[str] = None,
         dependencies: Sequence[params.Depends] = None,
         responses: Dict[Union[int, str], Dict[str, Any]] = None,
+        default_response_class: Optional[Type[Response]] = None,
     ) -> None:
         if prefix:
             assert prefix.startswith("/"), "A path prefix must start with '/'"
@@ -484,7 +482,7 @@ def include_router(
                     response_model_by_alias=route.response_model_by_alias,
                     response_model_skip_defaults=route.response_model_skip_defaults,
                     include_in_schema=route.include_in_schema,
-                    response_class=route.response_class,
+                    response_class=route.response_class or default_response_class,
                     name=route.name,
                 )
             elif isinstance(route, routing.Route):
@@ -523,10 +521,9 @@ def get(
         response_model_by_alias: bool = True,
         response_model_skip_defaults: bool = False,
         include_in_schema: bool = True,
-        response_class: Type[Response] = JSONResponse,
+        response_class: Type[Response] = None,
         name: str = None,
     ) -> Callable:
-
         return self.api_route(
             path=path,
             response_model=response_model,
@@ -568,7 +565,7 @@ def put(
         response_model_by_alias: bool = True,
         response_model_skip_defaults: bool = False,
         include_in_schema: bool = True,
-        response_class: Type[Response] = JSONResponse,
+        response_class: Type[Response] = None,
         name: str = None,
     ) -> Callable:
         return self.api_route(
@@ -612,7 +609,7 @@ def post(
         response_model_by_alias: bool = True,
         response_model_skip_defaults: bool = False,
         include_in_schema: bool = True,
-        response_class: Type[Response] = JSONResponse,
+        response_class: Type[Response] = None,
         name: str = None,
     ) -> Callable:
         return self.api_route(
@@ -656,7 +653,7 @@ def delete(
         response_model_by_alias: bool = True,
         response_model_skip_defaults: bool = False,
         include_in_schema: bool = True,
-        response_class: Type[Response] = JSONResponse,
+        response_class: Type[Response] = None,
         name: str = None,
     ) -> Callable:
         return self.api_route(
@@ -700,7 +697,7 @@ def options(
         response_model_by_alias: bool = True,
         response_model_skip_defaults: bool = False,
         include_in_schema: bool = True,
-        response_class: Type[Response] = JSONResponse,
+        response_class: Type[Response] = None,
         name: str = None,
     ) -> Callable:
         return self.api_route(
@@ -744,7 +741,7 @@ def head(
         response_model_by_alias: bool = True,
         response_model_skip_defaults: bool = False,
         include_in_schema: bool = True,
-        response_class: Type[Response] = JSONResponse,
+        response_class: Type[Response] = None,
         name: str = None,
     ) -> Callable:
         return self.api_route(
@@ -788,7 +785,7 @@ def patch(
         response_model_by_alias: bool = True,
         response_model_skip_defaults: bool = False,
         include_in_schema: bool = True,
-        response_class: Type[Response] = JSONResponse,
+        response_class: Type[Response] = None,
         name: str = None,
     ) -> Callable:
         return self.api_route(
@@ -832,7 +829,7 @@ def trace(
         response_model_by_alias: bool = True,
         response_model_skip_defaults: bool = False,
         include_in_schema: bool = True,
-        response_class: Type[Response] = JSONResponse,
+        response_class: Type[Response] = None,
         name: str = None,
     ) -> Callable:
         return self.api_route(
diff --git a/pyproject.toml b/pyproject.toml
index 942b0726864d8..06ca453d82f7d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -39,6 +39,7 @@ test = [
     "email_validator",
     "sqlalchemy",
     "databases[sqlite]",
+    "orjson"
 ]
 doc = [
     "mkdocs",
diff --git a/tests/test_default_response_class.py b/tests/test_default_response_class.py
new file mode 100644
index 0000000000000..4905945b55315
--- /dev/null
+++ b/tests/test_default_response_class.py
@@ -0,0 +1,216 @@
+from typing import Any
+
+import orjson
+from fastapi import APIRouter, FastAPI
+from starlette.responses import HTMLResponse, JSONResponse, PlainTextResponse
+from starlette.testclient import TestClient
+
+
+class ORJSONResponse(JSONResponse):
+    media_type = "application/x-orjson"
+
+    def render(self, content: Any) -> bytes:
+        return orjson.dumps(content)
+
+
+class OverrideResponse(JSONResponse):
+    media_type = "application/x-override"
+
+
+app = FastAPI(default_response_class=ORJSONResponse)
+router_a = APIRouter()
+router_a_a = APIRouter()
+router_a_b_override = APIRouter()  # Overrides default class
+router_b_override = APIRouter()  # Overrides default class
+router_b_a = APIRouter()
+router_b_a_c_override = APIRouter()  # Overrides default class again
+
+
+@app.get("/")
+def get_root():
+    return {"msg": "Hello World"}
+
+
+@app.get("/override", response_class=PlainTextResponse)
+def get_path_override():
+    return "Hello World"
+
+
+@router_a.get("/")
+def get_a():
+    return {"msg": "Hello A"}
+
+
+@router_a.get("/override", response_class=PlainTextResponse)
+def get_a_path_override():
+    return "Hello A"
+
+
+@router_a_a.get("/")
+def get_a_a():
+    return {"msg": "Hello A A"}
+
+
+@router_a_a.get("/override", response_class=PlainTextResponse)
+def get_a_a_path_override():
+    return "Hello A A"
+
+
+@router_a_b_override.get("/")
+def get_a_b():
+    return "Hello A B"
+
+
+@router_a_b_override.get("/override", response_class=HTMLResponse)
+def get_a_b_path_override():
+    return "Hello A B"
+
+
+@router_b_override.get("/")
+def get_b():
+    return "Hello B"
+
+
+@router_b_override.get("/override", response_class=HTMLResponse)
+def get_b_path_override():
+    return "Hello B"
+
+
+@router_b_a.get("/")
+def get_b_a():
+    return "Hello B A"
+
+
+@router_b_a.get("/override", response_class=HTMLResponse)
+def get_b_a_path_override():
+    return "Hello B A"
+
+
+@router_b_a_c_override.get("/")
+def get_b_a_c():
+    return "Hello B A C"
+
+
+@router_b_a_c_override.get("/override", response_class=OverrideResponse)
+def get_b_a_c_path_override():
+    return {"msg": "Hello B A C"}
+
+
+router_b_a.include_router(
+    router_b_a_c_override, prefix="/c", default_response_class=HTMLResponse
+)
+router_b_override.include_router(router_b_a, prefix="/a")
+router_a.include_router(router_a_a, prefix="/a")
+router_a.include_router(
+    router_a_b_override, prefix="/b", default_response_class=PlainTextResponse
+)
+app.include_router(router_a, prefix="/a")
+app.include_router(
+    router_b_override, prefix="/b", default_response_class=PlainTextResponse
+)
+
+
+client = TestClient(app)
+
+orjson_type = "application/x-orjson"
+text_type = "text/plain; charset=utf-8"
+html_type = "text/html; charset=utf-8"
+override_type = "application/x-override"
+
+
+def test_app():
+    with client:
+        response = client.get("/")
+    assert response.json() == {"msg": "Hello World"}
+    assert response.headers["content-type"] == orjson_type
+
+
+def test_app_override():
+    with client:
+        response = client.get("/override")
+    assert response.content == b"Hello World"
+    assert response.headers["content-type"] == text_type
+
+
+def test_router_a():
+    with client:
+        response = client.get("/a")
+    assert response.json() == {"msg": "Hello A"}
+    assert response.headers["content-type"] == orjson_type
+
+
+def test_router_a_override():
+    with client:
+        response = client.get("/a/override")
+    assert response.content == b"Hello A"
+    assert response.headers["content-type"] == text_type
+
+
+def test_router_a_a():
+    with client:
+        response = client.get("/a/a")
+    assert response.json() == {"msg": "Hello A A"}
+    assert response.headers["content-type"] == orjson_type
+
+
+def test_router_a_a_override():
+    with client:
+        response = client.get("/a/a/override")
+    assert response.content == b"Hello A A"
+    assert response.headers["content-type"] == text_type
+
+
+def test_router_a_b():
+    with client:
+        response = client.get("/a/b")
+    assert response.content == b"Hello A B"
+    assert response.headers["content-type"] == text_type
+
+
+def test_router_a_b_override():
+    with client:
+        response = client.get("/a/b/override")
+    assert response.content == b"Hello A B"
+    assert response.headers["content-type"] == html_type
+
+
+def test_router_b():
+    with client:
+        response = client.get("/b")
+    assert response.content == b"Hello B"
+    assert response.headers["content-type"] == text_type
+
+
+def test_router_b_override():
+    with client:
+        response = client.get("/b/override")
+    assert response.content == b"Hello B"
+    assert response.headers["content-type"] == html_type
+
+
+def test_router_b_a():
+    with client:
+        response = client.get("/b/a")
+    assert response.content == b"Hello B A"
+    assert response.headers["content-type"] == text_type
+
+
+def test_router_b_a_override():
+    with client:
+        response = client.get("/b/a/override")
+    assert response.content == b"Hello B A"
+    assert response.headers["content-type"] == html_type
+
+
+def test_router_b_a_c():
+    with client:
+        response = client.get("/b/a/c")
+    assert response.content == b"Hello B A C"
+    assert response.headers["content-type"] == html_type
+
+
+def test_router_b_a_c_override():
+    with client:
+        response = client.get("/b/a/c/override")
+    assert response.json() == {"msg": "Hello B A C"}
+    assert response.headers["content-type"] == override_type
diff --git a/tests/test_default_response_class_router.py b/tests/test_default_response_class_router.py
new file mode 100644
index 0000000000000..95aada4097df5
--- /dev/null
+++ b/tests/test_default_response_class_router.py
@@ -0,0 +1,206 @@
+from fastapi import APIRouter, FastAPI
+from starlette.responses import HTMLResponse, JSONResponse, PlainTextResponse
+from starlette.testclient import TestClient
+
+
+class OverrideResponse(JSONResponse):
+    media_type = "application/x-override"
+
+
+app = FastAPI()
+router_a = APIRouter()
+router_a_a = APIRouter()
+router_a_b_override = APIRouter()  # Overrides default class
+router_b_override = APIRouter()  # Overrides default class
+router_b_a = APIRouter()
+router_b_a_c_override = APIRouter()  # Overrides default class again
+
+
+@app.get("/")
+def get_root():
+    return {"msg": "Hello World"}
+
+
+@app.get("/override", response_class=PlainTextResponse)
+def get_path_override():
+    return "Hello World"
+
+
+@router_a.get("/")
+def get_a():
+    return {"msg": "Hello A"}
+
+
+@router_a.get("/override", response_class=PlainTextResponse)
+def get_a_path_override():
+    return "Hello A"
+
+
+@router_a_a.get("/")
+def get_a_a():
+    return {"msg": "Hello A A"}
+
+
+@router_a_a.get("/override", response_class=PlainTextResponse)
+def get_a_a_path_override():
+    return "Hello A A"
+
+
+@router_a_b_override.get("/")
+def get_a_b():
+    return "Hello A B"
+
+
+@router_a_b_override.get("/override", response_class=HTMLResponse)
+def get_a_b_path_override():
+    return "Hello A B"
+
+
+@router_b_override.get("/")
+def get_b():
+    return "Hello B"
+
+
+@router_b_override.get("/override", response_class=HTMLResponse)
+def get_b_path_override():
+    return "Hello B"
+
+
+@router_b_a.get("/")
+def get_b_a():
+    return "Hello B A"
+
+
+@router_b_a.get("/override", response_class=HTMLResponse)
+def get_b_a_path_override():
+    return "Hello B A"
+
+
+@router_b_a_c_override.get("/")
+def get_b_a_c():
+    return "Hello B A C"
+
+
+@router_b_a_c_override.get("/override", response_class=OverrideResponse)
+def get_b_a_c_path_override():
+    return {"msg": "Hello B A C"}
+
+
+router_b_a.include_router(
+    router_b_a_c_override, prefix="/c", default_response_class=HTMLResponse
+)
+router_b_override.include_router(router_b_a, prefix="/a")
+router_a.include_router(router_a_a, prefix="/a")
+router_a.include_router(
+    router_a_b_override, prefix="/b", default_response_class=PlainTextResponse
+)
+app.include_router(router_a, prefix="/a")
+app.include_router(
+    router_b_override, prefix="/b", default_response_class=PlainTextResponse
+)
+
+
+client = TestClient(app)
+
+json_type = "application/json"
+text_type = "text/plain; charset=utf-8"
+html_type = "text/html; charset=utf-8"
+override_type = "application/x-override"
+
+
+def test_app():
+    with client:
+        response = client.get("/")
+    assert response.json() == {"msg": "Hello World"}
+    assert response.headers["content-type"] == json_type
+
+
+def test_app_override():
+    with client:
+        response = client.get("/override")
+    assert response.content == b"Hello World"
+    assert response.headers["content-type"] == text_type
+
+
+def test_router_a():
+    with client:
+        response = client.get("/a")
+    assert response.json() == {"msg": "Hello A"}
+    assert response.headers["content-type"] == json_type
+
+
+def test_router_a_override():
+    with client:
+        response = client.get("/a/override")
+    assert response.content == b"Hello A"
+    assert response.headers["content-type"] == text_type
+
+
+def test_router_a_a():
+    with client:
+        response = client.get("/a/a")
+    assert response.json() == {"msg": "Hello A A"}
+    assert response.headers["content-type"] == json_type
+
+
+def test_router_a_a_override():
+    with client:
+        response = client.get("/a/a/override")
+    assert response.content == b"Hello A A"
+    assert response.headers["content-type"] == text_type
+
+
+def test_router_a_b():
+    with client:
+        response = client.get("/a/b")
+    assert response.content == b"Hello A B"
+    assert response.headers["content-type"] == text_type
+
+
+def test_router_a_b_override():
+    with client:
+        response = client.get("/a/b/override")
+    assert response.content == b"Hello A B"
+    assert response.headers["content-type"] == html_type
+
+
+def test_router_b():
+    with client:
+        response = client.get("/b")
+    assert response.content == b"Hello B"
+    assert response.headers["content-type"] == text_type
+
+
+def test_router_b_override():
+    with client:
+        response = client.get("/b/override")
+    assert response.content == b"Hello B"
+    assert response.headers["content-type"] == html_type
+
+
+def test_router_b_a():
+    with client:
+        response = client.get("/b/a")
+    assert response.content == b"Hello B A"
+    assert response.headers["content-type"] == text_type
+
+
+def test_router_b_a_override():
+    with client:
+        response = client.get("/b/a/override")
+    assert response.content == b"Hello B A"
+    assert response.headers["content-type"] == html_type
+
+
+def test_router_b_a_c():
+    with client:
+        response = client.get("/b/a/c")
+    assert response.content == b"Hello B A C"
+    assert response.headers["content-type"] == html_type
+
+
+def test_router_b_a_c_override():
+    with client:
+        response = client.get("/b/a/c/override")
+    assert response.json() == {"msg": "Hello B A C"}
+    assert response.headers["content-type"] == override_type