diff --git a/horizon/forms/views.py b/horizon/forms/views.py
index 8169405d6f..ca337ce6fd 100644
--- a/horizon/forms/views.py
+++ b/horizon/forms/views.py
@@ -20,6 +20,7 @@ from django import http
 from django.utils.translation import gettext_lazy as _
 
 from horizon import exceptions
+from horizon.utils import http as http_utils
 from horizon import views
 
 
@@ -59,7 +60,7 @@ class ModalBackdropMixin(object):
 
 class ModalFormMixin(ModalBackdropMixin):
     def get_template_names(self):
-        if self.request.is_ajax():
+        if http_utils.is_ajax(self.request):
             if not hasattr(self, "ajax_template_name"):
                 # Transform standard template name to ajax name (leading "_")
                 bits = list(os.path.split(self.template_name))
@@ -74,7 +75,7 @@ class ModalFormMixin(ModalBackdropMixin):
 
     def get_context_data(self, **kwargs):
         context = super().get_context_data(**kwargs)
-        if self.request.is_ajax():
+        if http_utils.is_ajax(self.request):
             context['hide'] = True
         if ADD_TO_FIELD_HEADER in self.request.META:
             context['add_to_field'] = self.request.META[ADD_TO_FIELD_HEADER]
diff --git a/horizon/messages.py b/horizon/messages.py
index 9e07b035ea..ea0c0e9b41 100644
--- a/horizon/messages.py
+++ b/horizon/messages.py
@@ -22,10 +22,12 @@ from django.contrib.messages import constants
 from django.utils.encoding import force_str
 from django.utils.safestring import SafeData
 
+from horizon.utils import http as http_utils
+
 
 def horizon_message_already_queued(request, message):
     _message = force_str(message)
-    if request.is_ajax():
+    if http_utils.is_ajax(request):
         for tag, msg, extra in request.horizon['async_messages']:
             if _message == msg:
                 return True
@@ -39,7 +41,7 @@ def horizon_message_already_queued(request, message):
 def add_message(request, level, message, extra_tags='', fail_silently=False):
     """Attempts to add a message to the request using the 'messages' app."""
     if not horizon_message_already_queued(request, message):
-        if request.is_ajax():
+        if http_utils.is_ajax(request):
             tag = constants.DEFAULT_TAGS[level]
             # if message is marked as safe, pass "safe" tag as extra_tags so
             # that client can skip HTML escape for the message when rendering
diff --git a/horizon/middleware/base.py b/horizon/middleware/base.py
index da55707da6..d5a806fecc 100644
--- a/horizon/middleware/base.py
+++ b/horizon/middleware/base.py
@@ -36,6 +36,7 @@ from django.utils import timezone
 
 from horizon import exceptions
 from horizon.utils import functions as utils
+from horizon.utils import http as http_utils
 
 
 LOG = logging.getLogger(__name__)
@@ -77,7 +78,7 @@ class HorizonMiddleware(object):
             session_time = min(timeout, int(token_life.total_seconds()))
             request.session.set_expiry(session_time)
 
-        if request.is_ajax():
+        if http_utils.is_ajax(request):
             # if the request is Ajax we do not want to proceed, as clients can
             #  1) create pages with constant polling, which can create race
             #     conditions when a page navigation occurs
@@ -140,7 +141,7 @@ class HorizonMiddleware(object):
                 return shortcuts.render(request, 'not_authorized.html',
                                         status=403)
 
-            if request.is_ajax():
+            if http_utils.is_ajax(request):
                 response_401 = http.HttpResponse(status=401)
                 response_401['X-Horizon-Location'] = response['location']
                 return response_401
@@ -166,7 +167,7 @@ class HorizonMiddleware(object):
 
         This is to allow ajax request to redirect url.
         """
-        if request.is_ajax() and hasattr(request, 'horizon'):
+        if http_utils.is_ajax(request) and hasattr(request, 'horizon'):
             queued_msgs = request.horizon['async_messages']
             if type(response) == http.HttpResponseRedirect:
                 # Drop our messages back into the session as per usual so they
diff --git a/horizon/tables/base.py b/horizon/tables/base.py
index 8de69623cd..4427d5383f 100644
--- a/horizon/tables/base.py
+++ b/horizon/tables/base.py
@@ -46,6 +46,7 @@ from horizon.tables.actions import BatchAction
 from horizon.tables.actions import FilterAction
 from horizon.tables.actions import LinkAction
 from horizon.utils import html
+from horizon.utils import http as http_utils
 from horizon.utils import settings as utils_settings
 
 
@@ -1684,7 +1685,7 @@ class DataTable(object, metaclass=DataTableMetaclass):
                 except Exception:
                     datum = None
                     error = exceptions.handle(request, ignore=True)
-                if request.is_ajax():
+                if http_utils.is_ajax(request):
                     if not error:
                         return HttpResponse(new_row.render())
                     return HttpResponse(status=error.status_code)
@@ -1744,7 +1745,7 @@ class DataTable(object, metaclass=DataTableMetaclass):
         except Exception:
             datum = None
             error = exceptions.handle(request, ignore=True)
-        if request.is_ajax():
+        if http_utils.is_ajax(request):
             if not error:
                 return HttpResponse(cell.render())
             return HttpResponse(status=error.status_code)
diff --git a/horizon/tabs/views.py b/horizon/tabs/views.py
index 7dc93cb039..99f2ae2b17 100644
--- a/horizon/tabs/views.py
+++ b/horizon/tabs/views.py
@@ -15,6 +15,7 @@ from django import http
 from horizon import exceptions
 from horizon import tables
 from horizon.tabs.base import TableTab
+from horizon.utils import http as http_utils
 from horizon import views
 
 
@@ -60,7 +61,7 @@ class TabView(views.HorizonTemplateView):
 
         Otherwise renders the response as normal.
         """
-        if self.request.is_ajax():
+        if http_utils.is_ajax(self.request):
             if tab_group.selected:
                 return http.HttpResponse(tab_group.selected.render())
             return http.HttpResponse(tab_group.render())
diff --git a/horizon/utils/http.py b/horizon/utils/http.py
new file mode 100644
index 0000000000..fbfa3b05ff
--- /dev/null
+++ b/horizon/utils/http.py
@@ -0,0 +1,28 @@
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+
+def is_ajax(request):
+    """Check if the request is AJAX-based.
+
+    :param request: django.http.HttpRequest object
+    :return: True if the request is AJAX-based.
+    """
+    # NOTE: Django 3.1 or later deprecates request.is_ajax() as it relied
+    # on a jQuery-specific way of signifying AJAX calls,
+    # but at the moment checking X-Requested-With header works in horizon.
+    # If we adopt modern frameworks with JavaScript Fetch API,
+    # we need to consider checking Accepts header as suggested in the
+    # Django 3.1 release notes.
+    # https://docs.djangoproject.com/en/4.0/releases/3.1/#id2
+    # https://docs.djangoproject.com/en/3.1/ref/request-response/#django.http.HttpRequest.is_ajax
+    return request.headers.get('x-requested-with') == 'XMLHttpRequest'
diff --git a/horizon/workflows/base.py b/horizon/workflows/base.py
index 4a553ead19..69003e26e8 100644
--- a/horizon/workflows/base.py
+++ b/horizon/workflows/base.py
@@ -35,6 +35,7 @@ from horizon import base
 from horizon import exceptions
 from horizon.templatetags.horizon import has_permissions
 from horizon.utils import html
+from horizon.utils import http as http_utils
 
 
 LOG = logging.getLogger(__name__)
@@ -904,7 +905,7 @@ class Workflow(html.HTMLElement, metaclass=WorkflowMetaclass):
         """Renders the workflow."""
         workflow_template = template.loader.get_template(self.template_name)
         extra_context = {"workflow": self}
-        if self.request.is_ajax():
+        if http_utils.is_ajax(self.request):
             extra_context['modal'] = True
         return workflow_template.render(extra_context, self.request)
 
diff --git a/horizon/workflows/views.py b/horizon/workflows/views.py
index 365de3f0f3..99eb1dac04 100644
--- a/horizon/workflows/views.py
+++ b/horizon/workflows/views.py
@@ -25,6 +25,7 @@ from horizon import exceptions
 from horizon.forms import views as hz_views
 from horizon.forms.views import ADD_TO_FIELD_HEADER
 from horizon import messages
+from horizon.utils import http as http_utils
 
 
 class WorkflowView(hz_views.ModalBackdropMixin, generic.TemplateView):
@@ -115,7 +116,7 @@ class WorkflowView(hz_views.ModalBackdropMixin, generic.TemplateView):
         The returned classes are determied based on
         the workflow characteristics.
         """
-        if self.request.is_ajax():
+        if http_utils.is_ajax(self.request):
             layout = ['modal', ]
         else:
             layout = ['static_page', ]
@@ -127,7 +128,7 @@ class WorkflowView(hz_views.ModalBackdropMixin, generic.TemplateView):
 
     def get_template_names(self):
         """Returns the template name to use for this request."""
-        if self.request.is_ajax():
+        if http_utils.is_ajax(self.request):
             template = self.ajax_template_name
         else:
             template = self.template_name
diff --git a/openstack_auth/views.py b/openstack_auth/views.py
index a342478744..3013289505 100644
--- a/openstack_auth/views.py
+++ b/openstack_auth/views.py
@@ -71,6 +71,13 @@ def set_logout_reason(res, msg):
     res.set_cookie('logout_reason', msg, max_age=10)
 
 
+def is_ajax(request):
+    # See horizon.utils.http.is_ajax() for more detail.
+    # NOTE: openstack_auth does not import modules from horizon to avoid
+    # import loops, so we copy the logic from horizon.utils.http.
+    return request.headers.get('x-requested-with') == 'XMLHttpRequest'
+
+
 # TODO(stephenfin): Migrate to CBV
 @sensitive_post_parameters()
 @csrf_protect
@@ -102,7 +109,7 @@ def login(request):
             url = utils.get_websso_url(request, auth_url, auth_type)
             return shortcuts.redirect(url)
 
-    if not request.is_ajax():
+    if not is_ajax(request):
         # If the user is already authenticated, redirect them to the
         # dashboard straight away, unless the 'next' parameter is set as it
         # usually indicates requesting access to a page that requires different
@@ -143,7 +150,7 @@ def login(request):
         'logout_status': logout_status,
     }
 
-    if request.is_ajax():
+    if is_ajax(request):
         template_name = 'auth/_login.html'
         extra_context['hide'] = True
     else:
diff --git a/openstack_dashboard/api/rest/utils.py b/openstack_dashboard/api/rest/utils.py
index 8073ffa4a0..5eb067999e 100644
--- a/openstack_dashboard/api/rest/utils.py
+++ b/openstack_dashboard/api/rest/utils.py
@@ -21,6 +21,7 @@ from django import http
 from oslo_serialization import jsonutils
 
 from horizon import exceptions
+from horizon.utils import http as http_utils
 
 LOG = logging.getLogger(__name__)
 
@@ -107,7 +108,7 @@ def ajax(authenticated=True, data_required=False,
         def _wrapped(self, request, *args, **kw):
             if authenticated and not request.user.is_authenticated:
                 return JSONResponse('not logged in', 401)
-            if not request.is_ajax():
+            if not http_utils.is_ajax(request):
                 return JSONResponse('request must be AJAX', 400)
 
             # decode the JSON body if present
diff --git a/openstack_dashboard/dashboards/project/volumes/views.py b/openstack_dashboard/dashboards/project/volumes/views.py
index 8ac0f164b8..d1a2027d20 100644
--- a/openstack_dashboard/dashboards/project/volumes/views.py
+++ b/openstack_dashboard/dashboards/project/volumes/views.py
@@ -33,6 +33,7 @@ from horizon import exceptions
 from horizon import forms
 from horizon import tables
 from horizon import tabs
+from horizon.utils import http as http_utils
 from horizon.utils import memoized
 
 from openstack_dashboard.api import cinder
@@ -566,7 +567,7 @@ class EditAttachmentsView(tables.DataTableView, forms.ModalFormView):
         else:
             context['show_attach'] = False
         context['volume'] = volume
-        if self.request.is_ajax():
+        if http_utils.is_ajax(self.request):
             context['hide'] = True
         return context
 
diff --git a/openstack_dashboard/test/helpers.py b/openstack_dashboard/test/helpers.py
index 5f0d72926d..9fcc49ff45 100644
--- a/openstack_dashboard/test/helpers.py
+++ b/openstack_dashboard/test/helpers.py
@@ -389,7 +389,6 @@ class TestCase(horizon_helpers.TestCase):
     def mock_rest_request(**args):
         mock_args = {
             'user.is_authenticated': True,
-            'is_ajax.return_value': True,
             'policy.check.return_value': True,
             'body': ''
         }
@@ -483,6 +482,12 @@ class APITestCase(TestCase):
         utils.patch_middleware_get_user()
 
 
+class RestAPITestCase(TestCase):
+    def setUp(self):
+        super().setUp()
+        mock.patch('horizon.utils.http.is_ajax', return_value=True).start()
+
+
 # APIMockTestCase was introduced to support mox to mock migration smoothly
 # but it turns we have still users of APITestCase.
 # We keep both for a while.
diff --git a/openstack_dashboard/test/unit/api/rest/test_cinder.py b/openstack_dashboard/test/unit/api/rest/test_cinder.py
index de6d28975f..030cd29632 100644
--- a/openstack_dashboard/test/unit/api/rest/test_cinder.py
+++ b/openstack_dashboard/test/unit/api/rest/test_cinder.py
@@ -20,7 +20,7 @@ from openstack_dashboard.test import helpers as test
 from openstack_dashboard.usage import quotas
 
 
-class CinderRestTestCase(test.TestCase):
+class CinderRestTestCase(test.RestAPITestCase):
 
     #
     # Volumes
diff --git a/openstack_dashboard/test/unit/api/rest/test_config.py b/openstack_dashboard/test/unit/api/rest/test_config.py
index c20054db5d..230dc211a1 100644
--- a/openstack_dashboard/test/unit/api/rest/test_config.py
+++ b/openstack_dashboard/test/unit/api/rest/test_config.py
@@ -18,7 +18,7 @@ from openstack_dashboard import api
 from openstack_dashboard.test import helpers as test
 
 
-class ConfigRestTestCase(test.TestCase):
+class ConfigRestTestCase(test.RestAPITestCase):
 
     @mock.patch.object(api.glance, 'get_image_schemas')
     def test_settings_config_get(self, mock_schemas_list):
diff --git a/openstack_dashboard/test/unit/api/rest/test_glance.py b/openstack_dashboard/test/unit/api/rest/test_glance.py
index b79ebbdbac..c36a8a31ca 100644
--- a/openstack_dashboard/test/unit/api/rest/test_glance.py
+++ b/openstack_dashboard/test/unit/api/rest/test_glance.py
@@ -19,7 +19,7 @@ from openstack_dashboard.api.rest import glance
 from openstack_dashboard.test import helpers as test
 
 
-class ImagesRestTestCase(test.ResetImageAPIVersionMixin, test.TestCase):
+class ImagesRestTestCase(test.ResetImageAPIVersionMixin, test.RestAPITestCase):
 
     def setUp(self):
         super().setUp()
diff --git a/openstack_dashboard/test/unit/api/rest/test_keystone.py b/openstack_dashboard/test/unit/api/rest/test_keystone.py
index a786fd8513..f9eb121b6e 100644
--- a/openstack_dashboard/test/unit/api/rest/test_keystone.py
+++ b/openstack_dashboard/test/unit/api/rest/test_keystone.py
@@ -22,7 +22,7 @@ from openstack_dashboard.api.rest import keystone
 from openstack_dashboard.test import helpers as test
 
 
-class KeystoneRestTestCase(test.TestCase):
+class KeystoneRestTestCase(test.RestAPITestCase):
 
     #
     # Version
diff --git a/openstack_dashboard/test/unit/api/rest/test_network.py b/openstack_dashboard/test/unit/api/rest/test_network.py
index 4b2b9f6b61..9482854e38 100644
--- a/openstack_dashboard/test/unit/api/rest/test_network.py
+++ b/openstack_dashboard/test/unit/api/rest/test_network.py
@@ -18,7 +18,7 @@ from openstack_dashboard.api.rest import network
 from openstack_dashboard.test import helpers as test
 
 
-class RestNetworkApiSecurityGroupTests(test.TestCase):
+class RestNetworkApiSecurityGroupTests(test.RestAPITestCase):
 
     @test.create_mocks({api.neutron: ['security_group_list']})
     def test_security_group_detailed(self):
@@ -34,7 +34,7 @@ class RestNetworkApiSecurityGroupTests(test.TestCase):
         self.mock_security_group_list.assert_called_once_with(request)
 
 
-class RestNetworkApiFloatingIpTests(test.TestCase):
+class RestNetworkApiFloatingIpTests(test.RestAPITestCase):
 
     @test.create_mocks({api.neutron: ['tenant_floating_ip_list']})
     def test_floating_ip_list(self):
diff --git a/openstack_dashboard/test/unit/api/rest/test_neutron.py b/openstack_dashboard/test/unit/api/rest/test_neutron.py
index 5c56eb7f25..5969e4712d 100644
--- a/openstack_dashboard/test/unit/api/rest/test_neutron.py
+++ b/openstack_dashboard/test/unit/api/rest/test_neutron.py
@@ -24,7 +24,7 @@ from openstack_dashboard.test import helpers as test
 from openstack_dashboard.usage import quotas
 
 
-class NeutronNetworksTestCase(test.TestCase):
+class NeutronNetworksTestCase(test.RestAPITestCase):
 
     def _dictify_network(self, network):
         net_dict = network.to_dict()
@@ -109,7 +109,7 @@ class NeutronNetworksTestCase(test.TestCase):
         mock_is_service_enabled.assert_called_once_with(request, 'network')
 
 
-class NeutronSubnetsTestCase(test.TestCase):
+class NeutronSubnetsTestCase(test.RestAPITestCase):
 
     @mock.patch.object(api.neutron, 'subnet_list')
     def test_get(self, mock_subnet_list):
@@ -141,7 +141,7 @@ class NeutronSubnetsTestCase(test.TestCase):
             network_id=network_id)
 
 
-class NeutronPortsTestCase(test.TestCase):
+class NeutronPortsTestCase(test.RestAPITestCase):
 
     @mock.patch.object(api.neutron, 'port_list_with_trunk_types')
     def test_get(self, mock_port_list_with_trunk_types):
@@ -155,7 +155,7 @@ class NeutronPortsTestCase(test.TestCase):
             request, network_id=network_id)
 
 
-class NeutronTrunkTestCase(test.TestCase):
+class NeutronTrunkTestCase(test.RestAPITestCase):
 
     @mock.patch.object(api.neutron, 'trunk_delete')
     def test_trunk_delete(self, mock_trunk_delete):
@@ -189,7 +189,7 @@ class NeutronTrunkTestCase(test.TestCase):
         )
 
 
-class NeutronTrunksTestCase(test.TestCase):
+class NeutronTrunksTestCase(test.RestAPITestCase):
 
     @mock.patch.object(api.neutron, 'trunk_list')
     def test_trunks_get(self, mock_trunk_list):
@@ -216,7 +216,7 @@ class NeutronTrunksTestCase(test.TestCase):
                                                   port_id='1')
 
 
-class NeutronExtensionsTestCase(test.TestCase):
+class NeutronExtensionsTestCase(test.RestAPITestCase):
 
     @mock.patch.object(api.neutron, 'list_extensions')
     def test_list_extensions(self, mock_list_extensions):
@@ -228,7 +228,7 @@ class NeutronExtensionsTestCase(test.TestCase):
         mock_list_extensions.assert_called_once_with(request)
 
 
-class NeutronDefaultQuotasTestCase(test.TestCase):
+class NeutronDefaultQuotasTestCase(test.RestAPITestCase):
 
     @test.create_mocks({api.base: ['is_service_enabled'],
                         api.neutron: ['tenant_quota_get']})
@@ -268,7 +268,7 @@ class NeutronDefaultQuotasTestCase(test.TestCase):
         mock_is_service_enabled.assert_called_once_with(request, 'network')
 
 
-class NeutronQuotaSetsTestCase(test.TestCase):
+class NeutronQuotaSetsTestCase(test.RestAPITestCase):
 
     @test.create_mocks({api.base: ['is_service_enabled'],
                         api.neutron: ['is_extension_supported',
diff --git a/openstack_dashboard/test/unit/api/rest/test_nova.py b/openstack_dashboard/test/unit/api/rest/test_nova.py
index 43feb97122..a7947c7193 100644
--- a/openstack_dashboard/test/unit/api/rest/test_nova.py
+++ b/openstack_dashboard/test/unit/api/rest/test_nova.py
@@ -39,7 +39,7 @@ class FakeFlavor(object):
         return {"id": self.id}
 
 
-class NovaRestTestCase(test.TestCase):
+class NovaRestTestCase(test.RestAPITestCase):
 
     #
     # Snapshots
diff --git a/openstack_dashboard/test/unit/api/rest/test_policy.py b/openstack_dashboard/test/unit/api/rest/test_policy.py
index 7896fe34a2..eb5b678742 100644
--- a/openstack_dashboard/test/unit/api/rest/test_policy.py
+++ b/openstack_dashboard/test/unit/api/rest/test_policy.py
@@ -11,6 +11,7 @@
 # limitations under the License.
 
 import json
+from unittest import mock
 
 from django.test.utils import override_settings
 
@@ -18,7 +19,7 @@ from openstack_dashboard.api.rest import policy
 from openstack_dashboard.test import helpers as test
 
 
-class PolicyRestTestCase(test.TestCase):
+class PolicyRestTestCase(test.RestAPITestCase):
 
     @override_settings(POLICY_CHECK_FUNCTION='openstack_auth.policy.check')
     def _test_policy(self, body, expected=True):
@@ -77,6 +78,14 @@ class PolicyRestTestCase(test.TestCase):
 
 
 class AdminPolicyRestTestCase(test.BaseAdminViewTests):
+
+    # NOTE: BaseAdminViewTests is used by other unit tests too,
+    # so mock for is_ajax() is prepared explicitly here.
+    # It should match horizon.test.helpers.RestAPITestCase.setUp().
+    def setUp(self):
+        super().setUp()
+        mock.patch('horizon.utils.http.is_ajax', return_value=True).start()
+
     @override_settings(POLICY_CHECK_FUNCTION='openstack_auth.policy.check')
     def test_rule_with_target(self):
         body = json.dumps(
diff --git a/openstack_dashboard/test/unit/api/rest/test_swift.py b/openstack_dashboard/test/unit/api/rest/test_swift.py
index c0c440216a..cf997e778f 100644
--- a/openstack_dashboard/test/unit/api/rest/test_swift.py
+++ b/openstack_dashboard/test/unit/api/rest/test_swift.py
@@ -18,7 +18,7 @@ from openstack_dashboard.api.rest import swift
 from openstack_dashboard.test import helpers as test
 
 
-class SwiftRestTestCase(test.TestCase):
+class SwiftRestTestCase(test.RestAPITestCase):
 
     #
     # Version
diff --git a/openstack_dashboard/test/unit/api/rest/test_utils.py b/openstack_dashboard/test/unit/api/rest/test_utils.py
index a5920d3711..2d96223e27 100644
--- a/openstack_dashboard/test/unit/api/rest/test_utils.py
+++ b/openstack_dashboard/test/unit/api/rest/test_utils.py
@@ -16,7 +16,7 @@ from openstack_dashboard.api.rest import utils
 from openstack_dashboard.test import helpers as test
 
 
-class RestUtilsTestCase(test.TestCase):
+class RestUtilsTestCase(test.RestAPITestCase):
 
     def test_api_success(self):
         @utils.ajax()
@@ -164,7 +164,7 @@ class RestUtilsTestCase(test.TestCase):
         self.assertDictEqual({}, output_filters)
 
 
-class JSONEncoderTestCase(test.TestCase):
+class JSONEncoderTestCase(test.RestAPITestCase):
 
     # NOTE(tsufiev): NaN numeric is "conventional" in a sense that the custom
     # NaNJSONEncoder encoder translates it to the same token that the standard