diff --git a/README.rst b/README.rst
index 7c8f9c5..aa960b8 100644
--- a/README.rst
+++ b/README.rst
@@ -52,6 +52,13 @@ You may also install the latest source from the
     pip install git+https://github.com/imacat/flask-digestauth.git
 
 
+Configuration
+=============
+
+Flask-DigestAuth takes the configuration ``DIGEST_AUTH_REALM`` as the
+realm.  The default realm is ``Login Required``.
+
+
 Setting the Password
 ====================
 
@@ -89,7 +96,7 @@ In your ``my_app.py``:
     app: flask = Flask(__name__)
     ... (Configure the Flask application) ...
 
-    auth: DigestAuth = DigestAuth(realm="Admin")
+    auth: DigestAuth = DigestAuth()
     auth.init_app(app)
 
     @auth.register_get_password
@@ -128,7 +135,6 @@ In your ``my_app/__init__.py``:
         app: flask = Flask(__name__)
         ... (Configure the Flask application) ...
 
-        auth.realm = app.config["REALM"]
         auth.init_app(app)
 
         @auth.register_get_password
@@ -207,7 +213,7 @@ In your ``my_app.py``:
     def load_user(user_id: str) -> t.Optional[User]:
         ... (Load the user with the username) ...
 
-    auth: DigestAuth = DigestAuth(realm="Admin")
+    auth: DigestAuth = DigestAuth()
     auth.init_app(app)
 
     @auth.register_get_password
@@ -251,7 +257,6 @@ In your ``my_app/__init__.py``:
         def load_user(user_id: str) -> t.Optional[User]:
             ... (Load the user with the username) ...
 
-        auth.realm = app.config["REALM"]
         auth.init_app(app)
 
         @auth.register_get_password
@@ -340,8 +345,9 @@ A unittest Test Case
 
         def create_app(self):
             app: Flask = create_app({
+                "TESTING": True,
                 "SECRET_KEY": token_urlsafe(32),
-                "TESTING": True
+                "DIGEST_AUTH_REALM": "admin",
             })
             app.test_client_class = Client
             return app
@@ -367,8 +373,9 @@ A pytest Test
     @pytest.fixture()
     def app():
         app: Flask = create_app({
+            "TESTING": True,
             "SECRET_KEY": token_urlsafe(32),
-            "TESTING": True
+            "DIGEST_AUTH_REALM": "admin",
         })
         app.test_client_class = Client
         yield app
diff --git a/docs/source/examples.rst b/docs/source/examples.rst
index c314537..5a6b1ca 100644
--- a/docs/source/examples.rst
+++ b/docs/source/examples.rst
@@ -17,7 +17,7 @@ In your ``my_app.py``:
     app: flask = Flask(__name__)
     ... (Configure the Flask application) ...
 
-    auth: DigestAuth = DigestAuth(realm="Admin")
+    auth: DigestAuth = DigestAuth()
     auth.init_app(app)
 
     @auth.register_get_password
@@ -58,7 +58,6 @@ In your ``my_app/__init__.py``:
         app: flask = Flask(__name__)
         ... (Configure the Flask application) ...
 
-        auth.realm = app.config["REALM"]
         auth.init_app(app)
 
         @auth.register_get_password
@@ -118,7 +117,7 @@ In your ``my_app.py``:
     def load_user(user_id: str) -> t.Optional[User]:
         ... (Load the user with the username) ...
 
-    auth: DigestAuth = DigestAuth(realm="Admin")
+    auth: DigestAuth = DigestAuth()
     auth.init_app(app)
 
     @auth.register_get_password
@@ -164,7 +163,6 @@ In your ``my_app/__init__.py``:
         def load_user(user_id: str) -> t.Optional[User]:
             ... (Load the user with the username) ...
 
-        auth.realm = app.config["REALM"]
         auth.init_app(app)
 
         @auth.register_get_password
@@ -219,8 +217,9 @@ A unittest Test Case
 
         def create_app(self):
             app: Flask = create_app({
+                "TESTING": True,
                 "SECRET_KEY": token_urlsafe(32),
-                "TESTING": True
+                "DIGEST_AUTH_REALM": "admin",
             })
             app.test_client_class = Client
             return app
@@ -249,8 +248,9 @@ A pytest Test
     @pytest.fixture()
     def app():
         app: Flask = create_app({
+            "TESTING": True,
             "SECRET_KEY": token_urlsafe(32),
-            "TESTING": True
+            "DIGEST_AUTH_REALM": "admin",
         })
         app.test_client_class = Client
         yield app
diff --git a/docs/source/intro.rst b/docs/source/intro.rst
index f5c9207..fdfc7f7 100644
--- a/docs/source/intro.rst
+++ b/docs/source/intro.rst
@@ -46,6 +46,13 @@ You may also install the latest source from the
     pip install git+https://github.com/imacat/flask-digestauth.git
 
 
+Configuration
+-------------
+
+Flask-DigestAuth takes the configuration ``DIGEST_AUTH_REALM`` as the
+realm.  The default realm is ``Login Required``.
+
+
 Setting the Password
 --------------------
 
diff --git a/src/flask_digest_auth/auth.py b/src/flask_digest_auth/auth.py
index 5b9b70b..417c5c0 100644
--- a/src/flask_digest_auth/auth.py
+++ b/src/flask_digest_auth/auth.py
@@ -46,8 +46,8 @@ class DigestAuth:
         self.__serializer: URLSafeTimedSerializer \
             = URLSafeTimedSerializer(token_urlsafe(32))
         """The serializer to generate and validate the nonce and opaque."""
-        self.realm: str = "" if realm is None else realm
-        """The realm.  Default is an empty string."""
+        self.realm: str = "Login Required" if realm is None else realm
+        """The realm.  Default is "Login Required"."""
         self.algorithm: t.Optional[t.Literal["MD5", "MD5-sess"]] = None
         """The algorithm, either None, ``MD5``, or ``MD5-sess``.  Default is
         None."""
@@ -343,6 +343,8 @@ class DigestAuth:
         :return: None.
         """
         app.extensions["digest_auth"] = self
+        if "DIGEST_AUTH_REALM" in app.config:
+            self.realm = app.config["DIGEST_AUTH_REALM"]
 
         if hasattr(app, "login_manager"):
             from flask_login import LoginManager, login_user
diff --git a/tests/test_auth.py b/tests/test_auth.py
index 5c7a4ec..02301cc 100644
--- a/tests/test_auth.py
+++ b/tests/test_auth.py
@@ -1,7 +1,7 @@
 # The Flask HTTP Digest Authentication Project.
 # Author: imacat@mail.imacat.idv.tw (imacat), 2022/10/22
 
-#  Copyright (c) 2022 imacat.
+#  Copyright (c) 2022-2023 imacat.
 #
 #  Licensed under the Apache License, Version 2.0 (the "License");
 #  you may not use this file except in compliance with the License.
@@ -59,10 +59,11 @@ class AuthenticationTestCase(TestCase):
         app.config.from_mapping({
             "TESTING": True,
             "SECRET_KEY": token_urlsafe(32),
+            "DIGEST_AUTH_REALM": _REALM,
         })
         app.test_client_class = Client
 
-        auth: DigestAuth = DigestAuth(realm=_REALM)
+        auth: DigestAuth = DigestAuth()
         auth.init_app(app)
         self.user: User = User(_USERNAME, _PASSWORD)
         user_db: t.Dict[str, User] = {_USERNAME: self.user}
diff --git a/tests/test_flask_login.py b/tests/test_flask_login.py
index b9a1971..e90c9b3 100644
--- a/tests/test_flask_login.py
+++ b/tests/test_flask_login.py
@@ -1,7 +1,7 @@
 # The Flask HTTP Digest Authentication Project.
 # Author: imacat@mail.imacat.idv.tw (imacat), 2022/11/23
 
-#  Copyright (c) 2022 imacat.
+#  Copyright (c) 2022-2023 imacat.
 #
 #  Licensed under the Apache License, Version 2.0 (the "License");
 #  you may not use this file except in compliance with the License.
@@ -79,6 +79,7 @@ class FlaskLoginTestCase(TestCase):
         app.config.from_mapping({
             "TESTING": True,
             "SECRET_KEY": token_urlsafe(32),
+            "DIGEST_AUTH_REALM": _REALM,
         })
         app.test_client_class = Client
 
@@ -92,7 +93,7 @@ class FlaskLoginTestCase(TestCase):
         login_manager: flask_login.LoginManager = flask_login.LoginManager()
         login_manager.init_app(app)
 
-        auth: DigestAuth = DigestAuth(realm=_REALM)
+        auth: DigestAuth = DigestAuth()
         auth.init_app(app)
 
         self.user: User = User(_USERNAME, _PASSWORD)