diff --git a/src/pretix/base/services/cart.py b/src/pretix/base/services/cart.py
index 14099b8c1..5212b1307 100644
--- a/src/pretix/base/services/cart.py
+++ b/src/pretix/base/services/cart.py
@@ -1655,7 +1655,7 @@ def clear_cart(self, event: Event, cart_id: str=None, locale='en', sales_channel
 
 
 @app.task(base=ProfiledEventTask, bind=True, max_retries=5, default_retry_delay=1, throws=(CartError,))
-def extend_cart_reservation(self, event: Event, cart_id: str=None, locale='en', sales_channel='web', override_now_dt: datetime=None) -> None:
+def extend_cart_reservation(self, event: Event, cart_id: str=None, locale='en', sales_channel='web', override_now_dt: datetime=None) -> dict:
     """
     Resets the expiry time of a cart to the configured reservation time of this event.
     Limited to 11x the reservation time.
@@ -1672,7 +1672,7 @@ def extend_cart_reservation(self, event: Event, cart_id: str=None, locale='en',
             try:
                 cm = CartManager(event=event, cart_id=cart_id, sales_channel=sales_channel)
                 cm.commit()
-                return cm.num_extended_positions
+                return {"success": cm.num_extended_positions, "expiry": cm._expiry, "max_expiry_extend": cm._max_expiry_extend}
             except LockTimeoutException:
                 self.retry()
         except (MaxRetriesExceededError, LockTimeoutException):
diff --git a/src/pretix/base/templatetags/dialog.py b/src/pretix/base/templatetags/dialog.py
index 16805cecc..0cc422455 100644
--- a/src/pretix/base/templatetags/dialog.py
+++ b/src/pretix/base/templatetags/dialog.py
@@ -23,38 +23,39 @@ from django import template
 from django.utils.html import format_html
 from django.utils.safestring import mark_safe
 
+from pretix.helpers.templatetags.simple_block_tag import (
+    register_simple_block_tag,
+)
+
 from django.utils.translation import gettext_lazy as _  # NOQA
 
+
 register = template.Library()
 
 
-@register.simple_tag
-def dialog(html_id, label, description, *args, **kwargs):
+@register_simple_block_tag(register)
+def dialog(content, html_id, title, description, *args, **kwargs):
     format_kwargs = {
         "id": html_id,
-        "label": label,
+        "title": title,
         "description": description,
         "icon": format_html('<div class="modal-card-icon"><span class="fa fa-{}" aria-hidden="true"></span></div>', kwargs["icon"]) if "icon" in kwargs else "",
         "alert": mark_safe('role="alertdialog"') if kwargs.get("alert", "False") != "False" else "",
+        "content": content,
     }
     result = """
     <dialog {alert}
-        id="{id}"
-        aria-labelledby="{id}-label"
+        id="{id}" class="modal-card"
+        aria-labelledby="{id}-title"
         aria-describedby="{id}-description">
-        <form method="dialog" class="modal-card form-horizontal">
+        <form method="dialog" class="modal-card-inner form-horizontal">
             {icon}
             <div class="modal-card-content">
-                <h2 id="{id}-label">{label}</h2>
-                <p id="{id}-description">{description}</p>
-    """
-    return format_html(result, **format_kwargs)
-
-
-@register.simple_tag
-def enddialog(*args, **kwargs):
-    return mark_safe("""
+                <h2 id="{id}-title" class="modal-card-title h3">{title}</h2>
+                <p id="{id}-description" class="modal-card-description">{description}</p>
+                {content}
             </div>
         </form>
     </dialog>
-    """)
+    """
+    return format_html(result, **format_kwargs)
diff --git a/src/pretix/base/views/tasks.py b/src/pretix/base/views/tasks.py
index 8a9e6e909..949cef639 100644
--- a/src/pretix/base/views/tasks.py
+++ b/src/pretix/base/views/tasks.py
@@ -68,7 +68,7 @@ class AsyncMixin:
     def get_check_url(self, task_id, ajax):
         return self.request.path + '?async_id=%s' % task_id + ('&ajax=1' if ajax else '')
 
-    def _ajax_response_data(self):
+    def _ajax_response_data(self, value):
         return {}
 
     def _return_ajax_result(self, res, timeout=.5):
@@ -85,7 +85,7 @@ class AsyncMixin:
                 logger.warning('Ignored ResponseError in AsyncResult.get()')
             except ConnectionError:
                 # Redis probably just restarted, let's just report not ready and retry next time
-                data = self._ajax_response_data()
+                data = self._ajax_response_data(None)
                 data.update({
                     'async_id': res.id,
                     'ready': False
@@ -93,7 +93,7 @@ class AsyncMixin:
                 return data
 
         state, info = res.state, res.info
-        data = self._ajax_response_data()
+        data = self._ajax_response_data(info)
         data.update({
             'async_id': res.id,
             'ready': ready,
@@ -102,23 +102,21 @@ class AsyncMixin:
         if ready:
             if state == states.SUCCESS and not isinstance(info, Exception):
                 smes = self.get_success_message(info)
-                if smes:
+                if smes and 'ajax_dont_redirect' not in self.request.GET and 'ajax_dont_redirect' not in self.request.POST:
                     messages.success(self.request, smes)
-                # TODO: Do not store message if the ajax client states that it will not redirect
-                # but handle the message itself
                 data.update({
                     'redirect': self.get_success_url(info),
                     'success': True,
-                    'message': str(self.get_success_message(info))
+                    'message': str(smes)
                 })
             else:
-                messages.error(self.request, self.get_error_message(info))
-                # TODO: Do not store message if the ajax client states that it will not redirect
-                # but handle the message itself
+                smes = self.get_error_message(info)
+                if smes and 'ajax_dont_redirect' not in self.request.GET and 'ajax_dont_redirect' not in self.request.POST:
+                    messages.error(self.request, smes)
                 data.update({
                     'redirect': self.get_error_url(),
                     'success': False,
-                    'message': str(self.get_error_message(info))
+                    'message': str(smes)
                 })
         elif state == 'PROGRESS':
             data.update({
diff --git a/src/pretix/control/templates/pretixcontrol/base.html b/src/pretix/control/templates/pretixcontrol/base.html
index 79d9c5f52..edd858c33 100644
--- a/src/pretix/control/templates/pretixcontrol/base.html
+++ b/src/pretix/control/templates/pretixcontrol/base.html
@@ -4,6 +4,8 @@
 {% load statici18n %}
 {% load eventsignal %}
 {% load eventurl %}
+{% load dialog %}
+{% load icon %}
 <!DOCTYPE html>
 <html{% if rtl %} dir="rtl" class="rtl"{% endif %}>
 	<head>
@@ -463,25 +465,16 @@
                 </div>
             </div>
         </div>
-        <div id="ajaxerr">
+        <div id="ajaxerr" class="modal-wrapper" hidden>
         </div>
-        <div id="loadingmodal">
-            <div class="modal-card">
-                <div class="modal-card-icon">
-                    <i class="fa fa-cog big-rotating-icon"></i>
-                </div>
-                <div class="modal-card-content">
-                    <h3></h3>
-                    <p class="text"></p>
-                    <p class="status">{% trans "If this takes longer than a few minutes, please contact us." %}</p>
-                    <div class="progress">
-                        <div class="progress-bar progress-bar-success">
-                        </div>
-                    </div>
-                    <div class="steps">
-                    </div>
+        {% dialog "loadingmodal" "" "" icon="cog rotating" %}
+            <p class="status">{% trans "If this takes longer than a few minutes, please contact us." %}</p>
+            <div class="progress">
+                <div class="progress-bar progress-bar-success">
                 </div>
             </div>
-        </div>
+            <div class="steps">
+            </div>
+        {% enddialog %}
 	</body>
 </html>
diff --git a/src/pretix/helpers/templatetags/simple_block_tag.py b/src/pretix/helpers/templatetags/simple_block_tag.py
new file mode 100644
index 000000000..a71bab7b0
--- /dev/null
+++ b/src/pretix/helpers/templatetags/simple_block_tag.py
@@ -0,0 +1,133 @@
+#
+# This file is part of pretix (Community Edition).
+#
+# Copyright (C) 2014-2020 Raphael Michel and contributors
+# Copyright (C) 2020-2021 rami.io GmbH and contributors
+#
+# This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General
+# Public License as published by the Free Software Foundation in version 3 of the License.
+#
+# ADDITIONAL TERMS APPLY: Pursuant to Section 7 of the GNU Affero General Public License, additional terms are
+# applicable granting you additional permissions and placing additional restrictions on your usage of this software.
+# Please refer to the pretix LICENSE file to obtain the full terms applicable to this work. If you did not receive
+# this file, see <https://pretix.eu/about/en/license>.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
+# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Affero General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Affero General Public License along with this program.  If not, see
+# <https://www.gnu.org/licenses/>.
+#
+
+#
+# backport from Django 5.2 (django/django/template/library.py)
+#
+# TODO: remove once we upgrade to Django 5.2
+
+from functools import wraps
+from inspect import getfullargspec, unwrap
+
+from django.template.exceptions import TemplateSyntaxError
+from django.template.library import SimpleNode, parse_bits
+
+
+class SimpleBlockNode(SimpleNode):
+    def __init__(self, nodelist, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.nodelist = nodelist
+
+    def get_resolved_arguments(self, context):
+        resolved_args, resolved_kwargs = super().get_resolved_arguments(context)
+
+        # Restore the "content" argument.
+        # It will move depending on whether takes_context was passed.
+        resolved_args.insert(
+            1 if self.takes_context else 0, self.nodelist.render(context)
+        )
+
+        return resolved_args, resolved_kwargs
+
+
+def register_simple_block_tag(library, func=None, takes_context=None, name=None, end_name=None):
+    """
+    Register a callable as a compiled block template tag. Example:
+
+    @register_simple_block_tag(register)
+    def hello(content):
+        return 'world'
+    """
+    def dec(func):
+        nonlocal end_name
+
+        (
+            params,
+            varargs,
+            varkw,
+            defaults,
+            kwonly,
+            kwonly_defaults,
+            _,
+        ) = getfullargspec(unwrap(func))
+        function_name = name or func.__name__
+
+        if end_name is None:
+            end_name = f"end{function_name}"
+
+        @wraps(func)
+        def compile_func(parser, token):
+            tag_params = params.copy()
+
+            if takes_context:
+                if len(tag_params) >= 2 and tag_params[1] == "content":
+                    del tag_params[1]
+                else:
+                    raise TemplateSyntaxError(
+                        f"{function_name!r} is decorated with takes_context=True so"
+                        " it must have a first argument of 'context' and a second "
+                        "argument of 'content'"
+                    )
+            elif tag_params and tag_params[0] == "content":
+                del tag_params[0]
+            else:
+                raise TemplateSyntaxError(
+                    f"'{function_name}' must have a first argument of 'content'"
+                )
+
+            bits = token.split_contents()[1:]
+            target_var = None
+            if len(bits) >= 2 and bits[-2] == "as":
+                target_var = bits[-1]
+                bits = bits[:-2]
+
+            nodelist = parser.parse((end_name,))
+            parser.delete_first_token()
+
+            args, kwargs = parse_bits(
+                parser,
+                bits,
+                tag_params,
+                varargs,
+                varkw,
+                defaults,
+                kwonly,
+                kwonly_defaults,
+                takes_context,
+                function_name,
+            )
+
+            return SimpleBlockNode(
+                nodelist, func, takes_context, args, kwargs, target_var
+            )
+
+        library.tag(function_name, compile_func)
+        return func
+
+    if func is None:
+        # @register.simple_block_tag(...)
+        return dec
+    elif callable(func):
+        # @register.simple_block_tag
+        return dec(func)
+    else:
+        raise ValueError("Invalid arguments provided to simple_block_tag")
diff --git a/src/pretix/presale/templates/pretixpresale/event/fragment_cart.html b/src/pretix/presale/templates/pretixpresale/event/fragment_cart.html
index bcfb67e9b..259b80f4b 100644
--- a/src/pretix/presale/templates/pretixpresale/event/fragment_cart.html
+++ b/src/pretix/presale/templates/pretixpresale/event/fragment_cart.html
@@ -495,7 +495,7 @@
         <form class="text-muted" id="cart-extend-form" data-asynctask data-asynctask-no-redirect
                 method="post" action="{% eventurl request.event "presale:event.cart.extend" cart_namespace=cart_namespace %}">
             {% csrf_token %}
-            <span id="cart-deadline" data-expires="{{ cart.first_expiry|date:"Y-m-d H:i:sO" }}" data-max-expiry-extend="{{ cart.max_expiry_extend|date:"Y-m-d H:i:sO" }}">
+            <p id="cart-deadline" data-expires="{{ cart.first_expiry|date:"Y-m-d H:i:sO" }}" data-max-expiry-extend="{{ cart.max_expiry_extend|date:"Y-m-d H:i:sO" }}">
                 {% if cart.minutes_left > 0 or cart.seconds_left > 0 %}
                     {% blocktrans trimmed with minutes=cart.minutes_left %}
                         The items in your cart are reserved for you for {{ minutes }} minutes.
@@ -503,9 +503,12 @@
                 {% else %}
                     {% trans "The items in your cart are no longer reserved for you. You can still complete your order as long as they’re available." %}
                 {% endif %}
-            </span>
-            <button class="btn btn-link" type="submit" id="cart-extend-button">
-                <i class="fa fa-refresh" aria-hidden="true"></i> {% trans "Extend" %}</button>
+            </p>
+            <p>
+                <button class="btn btn-default" type="submit" id="cart-extend-button" aria-describedby="cart-deadline">
+                    <i class="fa fa-refresh" aria-hidden="true"></i> {% trans "Extend reservation" %}
+                </button>
+            </p>
         </form>
     {% else %}
         <p class="sr-only" id="cart-description">{% trans "Overview of your ordered products." %}</p>
diff --git a/src/pretix/presale/templates/pretixpresale/event/fragment_cart_box.html b/src/pretix/presale/templates/pretixpresale/event/fragment_cart_box.html
index d1d94cdc1..934e98c92 100644
--- a/src/pretix/presale/templates/pretixpresale/event/fragment_cart_box.html
+++ b/src/pretix/presale/templates/pretixpresale/event/fragment_cart_box.html
@@ -4,7 +4,7 @@
 {% load rich_text %}
 {% load money %}
 <details class="panel {% if open %}panel-primary{% else %}panel-default{% endif %} cart" {% if open %}open{% endif %}>
-    <summary class="panel-heading">
+    <summary class="panel-heading" aria-describedby="cart-deadline">
         <h2 class="panel-title">
             <span>
                 <i class="fa fa-shopping-cart" aria-hidden="true"></i>
diff --git a/src/pretix/presale/templates/pretixpresale/fragment_modals.html b/src/pretix/presale/templates/pretixpresale/fragment_modals.html
index de6590c5c..fce9d0a05 100644
--- a/src/pretix/presale/templates/pretixpresale/fragment_modals.html
+++ b/src/pretix/presale/templates/pretixpresale/fragment_modals.html
@@ -4,18 +4,19 @@
 {% load escapejson %}
 {% load icon %}
 {% load dialog %}
-<div id="ajaxerr">
+<div id="ajaxerr" class="modal-wrapper" hidden>
 </div>
-<div id="popupmodal" hidden aria-live="polite">
+<div id="popupmodal" class="modal-wrapper" hidden aria-live="polite" role="dialog"
+        aria-labelledby="popupmodal-title">
     <div class="modal-card">
         <div class="modal-card-icon">
             <i class="fa fa-window-restore big-icon" aria-hidden="true"></i>
         </div>
         <div class="modal-card-content">
             <div>
-                <h3>
+                <h2 id="popupmodal-title" class="h3">
                     {% trans "We've started the requested process in a new window." %}
-                </h3>
+                </h2>
                 <p class="text">
                     {% trans "If you do not see the new window, we can help you launch it again." %}
                 </p>
@@ -32,20 +33,21 @@
         </div>
     </div>
 </div>
-<div id="loadingmodal" hidden aria-live="polite">
-    <div class="modal-card">
-        <div class="modal-card-icon">
-            <i class="fa fa-cog big-rotating-icon" aria-hidden="true"></i>
-        </div>
-        <div class="modal-card-content">
-            <h3 id="loadingmodal-label"></h3>
-            <div id="loadingmodal-description">
-                <p class="text"></p>
-                <p class="status">{% trans "If this takes longer than a few minutes, please contact us." %}</p>
-            </div>
+
+{% dialog "loadingmodal" "" "" icon="cog rotating" %}
+    <p class="status">{% trans "If this takes longer than a few minutes, please contact us." %}</p>
+    <div class="progress">
+        <div class="progress-bar progress-bar-success">
         </div>
     </div>
-</div>
+    <div class="steps">
+    </div>
+{% enddialog %}
+
+{% trans "Please let us know you're still there." as label_cart_extend_dialog %}
+{% dialog "dialog-cart-extend" label_cart_extend_dialog "" icon="clock-o" alert=true %}
+    <p class="modal-card-confirm"><button class="btn btn-lg btn-primary">{% trans "Continue" %}</button></p>
+{% enddialog %}
 
 <dialog id="lightbox-dialog" role="alertdialog" aria-labelledby="lightbox-label">
     <form method="dialog" class="modal-card">
diff --git a/src/pretix/presale/views/__init__.py b/src/pretix/presale/views/__init__.py
index 5b893c3dd..b8d6acb69 100644
--- a/src/pretix/presale/views/__init__.py
+++ b/src/pretix/presale/views/__init__.py
@@ -229,11 +229,13 @@ class CartMixin:
 
         try:
             first_expiry = min(p.expires for p in positions) if positions else now()
+            max_expiry_extend = min((p.max_extend for p in positions if p.max_extend), default=None)
             total_seconds_left = max(first_expiry - now(), timedelta()).total_seconds()
             minutes_left = int(total_seconds_left // 60)
             seconds_left = int(total_seconds_left % 60)
         except AttributeError:
             first_expiry = None
+            max_expiry_extend = None
             minutes_left = None
             seconds_left = None
 
@@ -250,6 +252,7 @@ class CartMixin:
             'minutes_left': minutes_left,
             'seconds_left': seconds_left,
             'first_expiry': first_expiry,
+            'max_expiry_extend': max_expiry_extend,
             'is_ordered': bool(order),
             'itemcount': sum(c.count for c in positions if not c.addon_to),
             'current_selected_payments': [p for p in self.current_selected_payments(total) if p.get('multi_use_supported')]
diff --git a/src/pretix/presale/views/cart.py b/src/pretix/presale/views/cart.py
index f99eac043..cb2533c8c 100644
--- a/src/pretix/presale/views/cart.py
+++ b/src/pretix/presale/views/cart.py
@@ -542,8 +542,14 @@ class CartExtendReservation(EventViewMixin, CartActionMixin, AsyncAction, View):
     task = extend_cart_reservation
     known_errortypes = ['CartError']
 
+    def _ajax_response_data(self, value):
+        if isinstance(value, dict):
+            return value
+        else:
+            return {}
+
     def get_success_message(self, value):
-        if value > 0:
+        if value['success'] > 0:
             return _('Your cart timeout was extended.')
 
     def post(self, request, *args, **kwargs):
@@ -561,7 +567,7 @@ class CartAdd(EventViewMixin, CartActionMixin, AsyncAction, View):
     def get_success_message(self, value):
         return _('The products have been successfully added to your cart.')
 
-    def _ajax_response_data(self):
+    def _ajax_response_data(self, value):
         cart_id = get_or_create_cart_id(self.request)
         return {
             'cart_id': cart_id,
diff --git a/src/pretix/static/pretixbase/js/asynctask.js b/src/pretix/static/pretixbase/js/asynctask.js
index dce4d6193..807e699d3 100644
--- a/src/pretix/static/pretixbase/js/asynctask.js
+++ b/src/pretix/static/pretixbase/js/asynctask.js
@@ -5,74 +5,94 @@ var async_task_check_url = null;
 var async_task_old_url = null;
 var async_task_is_download = false;
 var async_task_is_long = false;
+var async_task_dont_redirect = false;
 
-function async_task_check() {
+var async_task_status_messages = {
+    long_task_started: gettext(
+        'Your request is currently being processed. Depending on the size of your event, this might take up to ' +
+        'a few minutes.'
+    ),
+    long_task_pending: gettext(
+        'Your request has been queued on the server and will soon be ' +
+        'processed.'
+    ),
+    short_task: gettext(
+        'Your request arrived on the server but we still wait for it to be ' +
+        'processed. If this takes longer than two minutes, please contact us or go ' +
+        'back in your browser and try again.'
+    )
+};
+
+function async_task_schedule_check(context, timeout) {
     "use strict";
-    $.ajax(
-        {
-            'type': 'GET',
-            'url': async_task_check_url,
-            'success': async_task_check_callback,
-            'error': async_task_check_error,
-            'context': this,
-            'dataType': 'json'
+    async_task_timeout = window.setTimeout(function() {
+        $.ajax(
+            {
+                'type': 'GET',
+                'url': async_task_check_url,
+                'success': async_task_check_callback,
+                'error': async_task_check_error,
+                'context': context,
+                'dataType': 'json'
+            }
+        );
+    }, timeout);
+}
+
+function async_task_on_success(data) {
+    "use strict";
+    if ((async_task_is_download && data.success) || async_task_dont_redirect) {
+        waitingDialog.hide();
+        if (location.href.indexOf("async_id") !== -1) {
+            history.replaceState({}, "pretix", async_task_old_url);
         }
-    );
+    }
+    if (!async_task_dont_redirect)
+        location.href = data.redirect;
+    $(this).trigger('pretix:async-task-success', data);
 }
 
 function async_task_check_callback(data, textStatus, jqXHR) {
     "use strict";
     if (data.ready && data.redirect) {
-        if (async_task_is_download && data.success) {
-            waitingDialog.hide();
-            if (location.href.indexOf("async_id") !== -1) {
-                history.replaceState({}, "pretix", async_task_old_url);
-            }
-        }
-        location.href = data.redirect;
+        async_task_on_success.call(this, data);
         return;
-    } else if (typeof data.percentage === "number") {
-        $("#loadingmodal .progress").show();
-        $("#loadingmodal .progress .progress-bar").css("width", data.percentage + "%");
-        if (typeof data.steps === "object" && Array.isArray(data.steps)) {
-            var $steps = $("#loadingmodal .steps");
-            $steps.html("").show()
-            for (var step of data.steps) {
-                $steps.append(
-                    $("<span>").addClass("fa fa-fw")
-                        .toggleClass("fa-check text-success", step.done)
-                        .toggleClass("fa-cog fa-spin text-muted", !step.done)
-                ).append(
-                    $("<span>").text(step.label)
-                ).append(
-                    $("<br>")
-                )
-            }
-        }
     }
-    async_task_timeout = window.setTimeout(async_task_check, 250);
 
+    if (typeof data.percentage === "number") {
+        waitingDialog.setProgress(data.percentage);
+    }
+    if (typeof data.steps === "object" && Array.isArray(data.steps)) {
+        waitingDialog.setSteps(data.steps);
+    }
+    async_task_schedule_check(this, 250);
+
+    async_task_update_status(data);
+}
+
+function async_task_update_status(data) {
     if (async_task_is_long) {
         if (data.started) {
-            $("#loadingmodal p.status").text(gettext(
-                'Your request is currently being processed. Depending on the size of your event, this might take up to ' +
-                'a few minutes.'
-            ));
+            waitingDialog.setStatus(async_task_status_messages.long_task_started);
         } else {
-            $("#loadingmodal p.status").text(gettext(
-                'Your request has been queued on the server and will soon be ' +
-                'processed.'
-            ));
+            waitingDialog.setStatus(async_task_status_messages.long_task_pending);
         }
     } else {
-        $("#loadingmodal p.status").text(gettext(
-            'Your request arrived on the server but we still wait for it to be ' +
-            'processed. If this takes longer than two minutes, please contact us or go ' +
-            'back in your browser and try again.'
-        ));
+        waitingDialog.setStatus(async_task_status_messages.short_task);
     }
 }
 
+function async_task_replace_page(target, new_html) {
+    "use strict";
+    waitingDialog.hide();
+    $(target).html(new_html);
+    setup_basics($(target));
+    form_handlers($(target));
+    setup_collapsible_details($(target));
+    window.setTimeout(function () { $(window).scrollTop(0) }, 200)
+    $(document).trigger("pretix:bind-forms");
+}
+
 function async_task_check_error(jqXHR, textStatus, errorThrown) {
     "use strict";
     var respdom = $(jqXHR.responseText);
@@ -80,16 +100,10 @@ function async_task_check_error(jqXHR, textStatus, errorThrown) {
     if (respdom.filter('form') && (respdom.filter('.has-error') || respdom.filter('.alert-danger'))) {
         // This is a failed form validation, let's just use it
         $("body").data('ajaxing', false);
-        waitingDialog.hide();
-        $("body").html(jqXHR.responseText.substring(
+        async_task_replace_page("body", jqXHR.responseText.substring(
             jqXHR.responseText.indexOf("<body"),
             jqXHR.responseText.indexOf("</body")
         ));
-        setup_basics($("body"));
-        form_handlers($("body"));
-        setup_collapsible_details($("body"));
-        window.setTimeout(function () { $(window).scrollTop(0) }, 200)
-        $(document).trigger("pretix:bind-forms");
     } else if (c.length > 0) {
         // This is some kind of 500/404/403 page, show it in an overlay
         $("body").data('ajaxing', false);
@@ -105,9 +119,9 @@ function async_task_check_error(jqXHR, textStatus, errorThrown) {
             alert(gettext('An error of type {code} occurred.').replace(/\{code\}/, jqXHR.status));
         } else {
             // 500 can be an application error or overload in some cases :(
-            $("#loadingmodal p.status").text(gettext('We currently cannot reach the server, but we keep trying.' +
-                                              ' Last error code: {code}').replace(/\{code\}/, jqXHR.status));
-            async_task_timeout = window.setTimeout(async_task_check, 5000);
+            waitingDialog.setStatus(gettext('We currently cannot reach the server, but we keep trying.' +
+                                            ' Last error code: {code}').replace(/\{code\}/, jqXHR.status));
+            async_task_schedule_check(this, 5000);
         }
     }
 }
@@ -116,38 +130,19 @@ function async_task_callback(data, jqXHR, status) {
     "use strict";
     $("body").data('ajaxing', false);
     if (data.redirect) {
-        if (async_task_is_download && data.success) {
-            waitingDialog.hide();
-            if (location.href.indexOf("async_id") !== -1) {
-                history.replaceState({}, "pretix", async_task_old_url);
-            }
-        }
-        location.href = data.redirect;
+        async_task_on_success.call(this, data);
         return;
     }
-    async_task_id = data.async_id;
-    async_task_check_url = data.check_url;
-    async_task_timeout = window.setTimeout(async_task_check, 100);
-
-    if (async_task_is_long) {
-        if (data.started) {
-            $("#loadingmodal p.status").text(gettext(
-                'Your request is currently being processed. Depending on the size of your event, this might take up to ' +
-                'a few minutes.'
-            ));
-        } else {
-            $("#loadingmodal p.status").text(gettext(
-                'Your request has been queued on the server and will soon be ' +
-                'processed.'
-            ));
-        }
-    } else {
-        $("#loadingmodal p.status").text(gettext(
-            'Your request arrived on the server but we still wait for it to be ' +
-            'processed. If this takes longer than two minutes, please contact us or go ' +
-            'back in your browser and try again.'
-        ));
+    var check_url = new URL(data.check_url);
+    if (async_task_dont_redirect) {
+        check_url.searchParams.set('ajax_dont_redirect', '1');
     }
+    async_task_id = data.async_id;
+    async_task_check_url = check_url.toString();
+    async_task_schedule_check(this, 100);
+
+    async_task_update_status(data);
+
     if (location.href.indexOf("async_id") === -1) {
         history.pushState({}, "Waiting", async_task_check_url.replace(/ajax=1/, ''));
     }
@@ -156,48 +151,34 @@ function async_task_callback(data, jqXHR, status) {
 function async_task_error(jqXHR, textStatus, errorThrown) {
     "use strict";
     $("body").data('ajaxing', false);
+    waitingDialog.hide();
     if (textStatus === "timeout") {
         alert(gettext("The request took too long. Please try again."));
-        waitingDialog.hide();
     } else if (jqXHR.responseText.indexOf('<html') > 0) {
         var respdom = $(jqXHR.responseText);
         var c = respdom.filter('.container');
         if (respdom.filter('form') && (respdom.filter('.has-error') || respdom.filter('.alert-danger'))) {
             // This is a failed form validation, let's just use it
-            waitingDialog.hide();
 
             if (respdom.filter('#page-wrapper') && $('#page-wrapper').length) {
-                $("#page-wrapper").html(respdom.find("#page-wrapper").html());
-                setup_basics($("#page-wrapper"));
-                form_handlers($("#page-wrapper"));
-                setup_collapsible_details($("#page-wrapper"));
-                $(document).trigger("pretix:bind-forms");
-                window.setTimeout(function () { $(window).scrollTop(0) }, 200)
+                async_task_replace_page("#page-wrapper", respdom.find("#page-wrapper").html());
             } else {
-                $("body").html(jqXHR.responseText.substring(
+                async_task_replace_page("body", jqXHR.responseText.substring(
                     jqXHR.responseText.indexOf("<body"),
                     jqXHR.responseText.indexOf("</body")
                 ));
-                setup_basics($("body"));
-                form_handlers($("body"));
-                setup_collapsible_details($("body"));
-                $(document).trigger("pretix:bind-forms");
-                window.setTimeout(function () { $(window).scrollTop(0) }, 200)
             }
 
         } else if (c.length > 0) {
-            waitingDialog.hide();
+            // This is some kind of 500/404/403 page, show it in an overlay
             ajaxErrDialog.show(c.first().html());
         } else {
-            waitingDialog.hide();
             alert(gettext('An error of type {code} occurred.').replace(/\{code\}/, jqXHR.status));
         }
     } else {
         if (jqXHR.status >= 400 && jqXHR.status < 500) {
-            waitingDialog.hide();
             alert(gettext('An error of type {code} occurred.').replace(/\{code\}/, jqXHR.status));
         } else {
-            waitingDialog.hide();
             alert(gettext('We currently cannot reach the server. Please try again. ' +
                           'Error code: {code}').replace(/\{code\}/, jqXHR.status));
         }
@@ -221,28 +202,26 @@ $(function () {
         }
         async_task_id = null;
         async_task_is_download = $(this).is("[data-asynctask-download]");
+        async_task_dont_redirect = $(this).is("[data-asynctask-no-redirect]");
         async_task_is_long = $(this).is("[data-asynctask-long]");
         async_task_old_url = location.href;
         $("body").data('ajaxing', true);
-        if ($(this).is("[data-asynctask-headline]")) {
-            waitingDialog.show($(this).attr("data-asynctask-headline"));
-        } else {
-            waitingDialog.show(gettext('We are processing your request …'));
-        }
-        if ($(this).is("[data-asynctask-text]")) {
-            $("#loadingmodal p.text").text($(this).attr("data-asynctask-text")).show();
-        } else {
-            $("#loadingmodal p.text").hide();
-        }
-        $("#loadingmodal p.status").text(gettext(
-            'We are currently sending your request to the server. If this takes longer ' +
-            'than one minute, please check your internet connection and then reload ' +
-            'this page and try again.'
-        ));
+        waitingDialog.show(
+            $(this).attr("data-asynctask-headline") || gettext('We are processing your request …'),
+            $(this).attr("data-asynctask-text") || '',
+            gettext(
+                'We are currently sending your request to the server. If this takes longer ' +
+                'than one minute, please check your internet connection and then reload ' +
+                'this page and try again.'
+            )
+        );
 
         var action = this.action;
         var formData = new FormData(this);
         formData.append('ajax', '1');
+        if (async_task_dont_redirect) {
+            formData.append('ajax_dont_redirect', '1');
+        }
         if (submitter && submitter.name) {
             formData.append(submitter.name, submitter.value);
         }
@@ -275,21 +254,66 @@ $(function () {
             }, 10);
         }
     }, false);
+
+    $("#ajaxerr").on("click", ".ajaxerr-close", ajaxErrDialog.hide);
+    $("#loadingmodal").on("cancel", function() {
+        return false;
+    });
+    $("#loadingmodal").prop("closedBy", "none");
 });
 
 var waitingDialog = {
-    show: function (message) {
+    show: function (title, text, status) {
         "use strict";
-        $("#loadingmodal h3").html(message);
-        $("#loadingmodal .progress").hide();
-        $("#loadingmodal .steps").hide();
-        $("body").addClass("loading");
-        $("#loadingmodal").removeAttr("hidden");
+        this.setTitle(title);
+        this.setText(text);
+        this.setStatus(status || gettext('If this takes longer than a few minutes, please contact us.'));
+        this.setProgress(null);
+        this.setSteps(null);
+        document.getElementById("loadingmodal").showModal();
     },
     hide: function () {
         "use strict";
-        $("body").removeClass("loading");
-        $("#loadingmodal").attr("hidden", true);
+        document.getElementById("loadingmodal").close();
+    },
+    setTitle: function(title) {
+        $("#loadingmodal .modal-card-title").text(title);
+    },
+    setStatus: function(statusText) {
+        $("#loadingmodal p.status").text(statusText);
+    },
+    setText: function(text) {
+        if (text)
+            $("#loadingmodal .modal-card-description").text(text).show();
+        else
+            $("#loadingmodal .modal-card-description").hide();
+    },
+    setProgress: function(percentage) {
+        if (typeof percentage === 'number') {
+            $("#loadingmodal .progress").show();
+            $("#loadingmodal .progress .progress-bar").css("width", percentage + "%");
+        } else {
+            $("#loadingmodal .progress").hide();
+        }
+    },
+    setSteps: function(steps) {
+        var $steps = $("#loadingmodal .steps");
+        if (steps) {
+            $steps.html("").show()
+            for (var step of steps) {
+                $steps.append(
+                    $("<span>").addClass("fa fa-fw")
+                        .toggleClass("fa-check text-success", step.done)
+                        .toggleClass("fa-cog fa-spin text-muted", !step.done)
+                ).append(
+                    $("<span>").text(step.label)
+                ).append(
+                    $("<br>")
+                )
+            }
+        } else {
+            $steps.hide();
+        }
     }
 };
 
@@ -299,10 +323,10 @@ var ajaxErrDialog = {
         $("#ajaxerr").html(c);
         $("#ajaxerr .links").html("<a class='btn btn-default ajaxerr-close'>"
                                   + gettext("Close message") + "</a>");
-        $("body").addClass("ajaxerr");
+        $("body").addClass("ajaxerr has-modal-dialog");
     },
     hide: function () {
         "use strict";
-        $("body").removeClass("ajaxerr");
-    }
+        $("body").removeClass("ajaxerr has-modal-dialog");
+    },
 };
diff --git a/src/pretix/static/pretixbase/scss/_dialogs.scss b/src/pretix/static/pretixbase/scss/_dialogs.scss
new file mode 100644
index 000000000..33d11145c
--- /dev/null
+++ b/src/pretix/static/pretixbase/scss/_dialogs.scss
@@ -0,0 +1,174 @@
+/* Modal dialogs using HTML5 dialog tags for accessibility */
+dialog.modal-card {
+  border: none;
+  width: 80%;
+  max-width: 43em;
+  padding: 0;
+  margin-top: 60px;
+  box-shadow: 0 7px 14px 0 rgba(78, 50, 92, 0.1),0 3px 6px 0 rgba(0,0,0,.07);
+  background: white;
+  border-radius: $border-radius-large;
+
+  opacity: 0;
+  transition: opacity .5s allow-discrete;
+}
+.modal-card-inner {
+  display: flex;
+  flex-direction: column;
+  align-content: stretch;
+}
+dialog.modal-card .modal-card-icon {
+  background: $brand-primary;
+  font-size: 2em;
+  color: white;
+  text-align: center;
+  padding: 3px;
+  .rotating {
+      -webkit-animation: fa-spin 8s infinite linear;
+      animation: fa-spin 8s infinite linear;
+  }
+}
+dialog.modal-card .modal-card-content {
+  padding: 1.5em;
+  flex-grow: 1;
+}
+.modal-card-content>*:last-child {
+  margin-bottom: 0;
+}
+.modal-card-content>*:first-child {
+  margin-top: 0;
+}
+
+.modal-card-confirm {
+  margin-top: 2em;
+  display: flex;
+  justify-content: flex-end;
+  gap: 1em;
+  align-items: center;
+}
+.modal-card-confirm-spread {
+  justify-content: space-between;
+}
+
+dialog::backdrop {
+  background-color: rgba(255, 255, 255, .5);
+  opacity: 0;
+  transition: opacity .5s allow-discrete;
+  backdrop-filter: blur(2px);
+}
+dialog[open], dialog[open]::backdrop {
+  opacity: 1;
+}
+@starting-style {
+  dialog[open], dialog[open]::backdrop  {
+    opacity: 0;
+  }
+}
+
+@media screen and (min-width: $screen-sm-min) {
+  dialog.modal-card:has(.modal-card-icon) .modal-card-inner {
+    flex-direction: row;
+  }
+  dialog.modal-card .modal-card-content {
+    padding: 2em;
+  }
+  dialog.modal-card .modal-card-icon {
+    font-size: 4em;
+    padding: 6px 16px;
+  }
+}
+
+.shake-once {
+  animation: shake .2s;
+  transform: translate3d(0, 0, 0);
+  backface-visibility: hidden;
+}
+
+@keyframes shake {
+  0% { transform: skewX(0deg); }
+  20% { transform: skewX(-5deg); }
+  40% { transform: skewX(5deg); }
+  60% { transform: skewX(-5deg); }
+  80% { transform: skewX(5deg); }
+  100% { transform: skewX(0deg); }
+}
+
+
+
+/* Legacy dialogs (still used for #ajaxerr and #popupmodal) */
+body.has-modal-dialog .container, body.has-modal-dialog #wrapper {
+    -webkit-filter: blur(2px);
+    -moz-filter: blur(2px);
+    -ms-filter: blur(2px);
+    -o-filter: blur(2px);
+    filter: blur(2px);
+}
+
+.modal-wrapper {
+    position: fixed;
+    top: 0;
+    left: 0;
+    width: 100vw;
+    height: 100vh;
+    background: rgba(255, 255, 255, .7);
+    z-index: 900000;
+    padding: 10px;
+  .modal-card {
+      margin: 50px auto 0;
+      width: 90%;
+      max-width: 600px;
+      max-height: calc(100vh - 100px);
+      overflow-y: auto;
+      background: white;
+      border-radius: $border-radius-large;
+      box-shadow: 0 7px 14px 0 rgba(78, 50, 92, 0.1),0 3px 6px 0 rgba(0,0,0,.07);
+      padding: 20px;
+      min-height: 160px;
+      border: 0;
+
+      .modal-card-icon {
+          float: left;
+          width: 150px;
+          text-align: center;
+          .big-icon {
+              margin-top: 10px;
+              font-size: 100px;
+              color: $brand-primary;
+          }
+      }
+      .modal-card-content {
+          margin-left: 160px;
+          text-align: left;
+          h3 {
+              margin-top: 0;
+          }
+      }
+  }
+}
+
+@media (max-width: 700px) {
+    .modal-wrapper .modal-card {
+        margin: 25px auto 0;
+        max-height: calc(100vh - 50px - 20px);
+        .modal-card-icon {
+            float: none;
+            width: 100%;
+        }
+        .modal-card-content {
+            text-align: center;
+            margin-left: 0;
+            margin-right: 0;
+            margin-top: 10px;
+        }
+    }
+}
+
+#ajaxerr {
+    background: rgba(236, 236, 236, .9);
+
+    .big-icon {
+        margin-top: 50px;
+        font-size: 200px;
+        color: $brand-primary;
+    }
+}
diff --git a/src/pretix/static/pretixbase/scss/_theme.scss b/src/pretix/static/pretixbase/scss/_theme.scss
index d64e8a744..3a5423d41 100644
--- a/src/pretix/static/pretixbase/scss/_theme.scss
+++ b/src/pretix/static/pretixbase/scss/_theme.scss
@@ -263,117 +263,3 @@ svg.svg-icon {
 @include table-row-variant('warning', var(--pretix-brand-warning-lighten-40), var(--pretix-brand-warning-lighten-35));
 @include table-row-variant('danger', var(--pretix-brand-danger-lighten-30), var(--pretix-brand-danger-lighten-25));
 
-
-
-
-dialog {
-  border: none;
-  width: 80%;
-  max-width: 43em;
-  padding: 0;
-  box-shadow: 0 7px 14px 0 rgba(78, 50, 92, 0.1),0 3px 6px 0 rgba(0,0,0,.07);
-  background: white;
-  border-radius: $border-radius-large;
-
-  opacity: 0;
-  transition: opacity .5s allow-discrete;
-
-  .modal-card {
-    display: flex;
-    flex-direction: column;
-    align-content: stretch;
-  }
-  .modal-card-icon {
-    background: $brand-primary;
-    font-size: 2em;
-    color: white;
-    text-align: center;
-    padding: 3px;
-  }
-  .modal-card-content {
-    padding: 1.5em;
-  }
-  .modal-card-content>*:last-child {
-    margin-bottom: 0;
-  }
-  .modal-card-content>*:first-child {
-    margin-top: 0;
-  }
-
-  .modal-card-confirm {
-    margin-top: 2em;
-    display: flex;
-    justify-content: flex-end;
-    gap: 1em;
-    align-items: center;
-  }
-  .modal-card-confirm-spread {
-    justify-content: space-between;
-  }
-}
-dialog::backdrop {
-  background-color: rgba(255, 255, 255, .5);
-  opacity: 0;
-  transition: opacity .5s allow-discrete;
-}
-dialog[open], dialog[open]::backdrop {
-  opacity: 1;
-}
-@starting-style {
-  dialog[open], dialog[open]::backdrop  {
-    opacity: 0;
-  }
-}
-
-@media screen and (min-width: $screen-sm-min) {
-  dialog {
-    .modal-card:has(.modal-card-icon) {
-      flex-direction: row;
-    }
-    .modal-card-content {
-      padding: 2em;
-    }
-    .modal-card-icon {
-      font-size: 4em;
-      padding: 6px 16px;
-    }
-  }
-}
-
-.shake-once {
-  animation: shake .2s;
-  transform: translate3d(0, 0, 0);
-  backface-visibility: hidden;
-}
-
-@keyframes shake {
-  0% { transform: skewX(0deg); }
-  20% { transform: skewX(-5deg); }
-  40% { transform: skewX(5deg); }
-  60% { transform: skewX(-5deg); }
-  80% { transform: skewX(5deg); }
-  100% { transform: skewX(0deg); }
-}
-
-#lightbox-dialog {
-  width: fit-content;
-  max-width: 80%;
-  min-width: 24em;
-  .modal-card-content {
-    padding: 2.5em;
-  }
-
-  img {
-    max-width: 100%;
-  }
-
-  button {
-    position: absolute;
-    top: 1em;
-    right: 1em;
-  }
-  figcaption {
-    margin-top: 1em;
-  }
-}
-
diff --git a/src/pretix/static/pretixcontrol/js/ui/main.js b/src/pretix/static/pretixcontrol/js/ui/main.js
index 9f3e3ddf6..c93616c8a 100644
--- a/src/pretix/static/pretixcontrol/js/ui/main.js
+++ b/src/pretix/static/pretixcontrol/js/ui/main.js
@@ -51,32 +51,6 @@ function formatPrice(price, currency, locale) {
     }
 }
 
-var waitingDialog = {
-    show: function (message) {
-        "use strict";
-        $("#loadingmodal").find("h1").html(message);
-        $("body").addClass("loading");
-    },
-    hide: function () {
-        "use strict";
-        $("body").removeClass("loading");
-    }
-};
-
-var ajaxErrDialog = {
-    show: function (c) {
-        "use strict";
-        $("#ajaxerr").html(c);
-        $("#ajaxerr .links").html("<a class='btn btn-default ajaxerr-close'>"
-            + gettext("Close message") + "</a>");
-        $("body").addClass("ajaxerr");
-    },
-    hide: function () {
-        "use strict";
-        $("body").removeClass("ajaxerr");
-    }
-};
-
 var apiGET = function (url, callback) {
     $.getJSON(url, function (data) {
         callback(data);
diff --git a/src/pretix/static/pretixcontrol/scss/main.scss b/src/pretix/static/pretixcontrol/scss/main.scss
index 9a3892032..be9756f39 100644
--- a/src/pretix/static/pretixcontrol/scss/main.scss
+++ b/src/pretix/static/pretixcontrol/scss/main.scss
@@ -3,6 +3,7 @@
 @import "../../bootstrap/scss/_bootstrap.scss";
 @import "../../fontawesome/scss/font-awesome.scss";
 @import "../../pretixbase/scss/_theme.scss";
+@import "../../pretixbase/scss/_dialogs.scss";
 @import "../../typeahead/typeahead.scss";
 @import "../../charts/morris.scss";
 @import "../../cropper/cropper.scss";
@@ -234,91 +235,6 @@ p.bigger {
     }
 }
 
-body.loading #wrapper {
-    -webkit-filter: blur(2px);
-    -moz-filter: blur(2px);
-    -ms-filter: blur(2px);
-    -o-filter: blur(2px);
-    filter: blur(2px);
-}
-
-#loadingmodal, #ajaxerr {
-    position: fixed;
-    top: 0;
-    left: 0;
-    width: 100vw;
-    height: 100vh;
-    background: rgba(255, 255, 255, .7);
-    opacity: 0;
-    z-index: 900000;
-    visibility: hidden;
-    padding: 10px;
-
-    .big-icon {
-        margin-top: 50px;
-        font-size: 200px;
-        color: $brand-primary;
-    }
-
-    .modal-card {
-        margin: 50px auto 0;
-        top: 50px;
-        width: 90%;
-        max-width: 600px;
-        background: white;
-        border-radius: $border-radius-large;
-        box-shadow: 0 7px 14px 0 rgba(78, 50, 92, 0.1),0 3px 6px 0 rgba(0,0,0,.07);
-        padding: 20px;
-        min-height: 160px;
-
-        .modal-card-icon {
-            float: left;
-            width: 150px;
-            text-align: center;
-
-            .big-rotating-icon {
-                font-size: 120px;
-                margin: 0;
-            }
-        }
-        .modal-card-content {
-            margin-left: 160px;
-            text-align: left;
-            h3 {
-                margin-top: 0;
-            }
-        }
-    }
-}
-@media (max-width: 700px) {
-    #loadingmodal, #ajaxerr {
-        .modal-card {
-            .modal-card-icon {
-                float: none;
-                width: 100%;
-            }
-            .modal-card-content {
-                text-align: center;
-                margin-left: 0;
-                margin-right: 0;
-                margin-top: 10px;
-            }
-        }
-    }
-}
-
-#ajaxerr {
-    background: rgba(236, 236, 236, .9);
-}
-
-.loading #loadingmodal, .ajaxerr #ajaxerr {
-    opacity: 1;
-    visibility: visible;
-    transition: opacity .5s ease-in-out;
-    -moz-transition: opacity .5s ease-in-out;
-    -webkit-transition: opacity .5s ease-in-out;
-}
-
 .big-rotating-icon {
     margin-top: 50px;
     -webkit-animation: fa-spin 8s infinite linear;
diff --git a/src/pretix/static/pretixpresale/js/ui/cart.js b/src/pretix/static/pretixpresale/js/ui/cart.js
index bdb4b14c5..6128a2b2f 100644
--- a/src/pretix/static/pretixpresale/js/ui/cart.js
+++ b/src/pretix/static/pretixpresale/js/ui/cart.js
@@ -1,9 +1,11 @@
 /*global $,gettext,ngettext */
 var cart = {
     _deadline: null,
-    _deadline_interval: null,
+    _deadline_timeout: null,
     _deadline_call: 0,
     _time_offset: 0,
+    _prev_diff_minutes: 0,
+    _renewed_message: "",
 
     _get_now: function () {
         return moment().add(cart._time_offset, 'ms');
@@ -20,7 +22,12 @@ var cart = {
         cart._time_offset = server_time - client_time;
     },
 
-    draw_deadline: function () {
+    show_expiry_notification: function () {
+        document.getElementById("dialog-cart-extend").showModal();
+        cart._expiry_notified = true;
+    },
+
+    draw_deadline: function (renewed="") {
         function pad(n, width, z) {
             z = z || '0';
             n = n + '';
@@ -33,36 +40,73 @@ var cart = {
             return;
         }
         var now = cart._get_now();
-        var diff_minutes = Math.floor(cart._deadline.diff(now) / 1000 / 60);
-        var diff_seconds = Math.floor(cart._deadline.diff(now) / 1000 % 60);
-
-        if (diff_minutes < 2 || diff_minutes == 5) $("#cart-deadline").get(0).setAttribute("aria-live", "polite");
-        else $("#cart-deadline").get(0).removeAttribute("aria-live");
+        var diff_total_seconds = cart._deadline.diff(now) / 1000;
+        var diff_minutes = Math.floor(diff_total_seconds / 60);
+        var diff_seconds = Math.floor(diff_total_seconds % 60);
 
         if (diff_minutes < 0) {
             $("#cart-deadline").text(gettext("The items in your cart are no longer reserved for you. You can still complete your order as long as they’re available."));
             $("#cart-deadline-short").text(
                 gettext("Cart expired")
             );
-            window.clearInterval(cart._deadline_interval);
+            if (!cart._deadline_timeout) {
+                // no timeout => first time draw_deadline is invoked, but cart already expired => do not show dialog
+                cart._expiry_notified = true;
+            }
         } else {
-            $("#cart-deadline").text(ngettext(
-                "The items in your cart are reserved for you for one minute.",
-                "The items in your cart are reserved for you for {num} minutes.",
-                diff_minutes
-            ).replace(/\{num\}/g, diff_minutes));
+            if (diff_minutes !== cart._prev_diff_minutes) {
+                if (diff_minutes == 0) {
+                    $("#cart-deadline").text(gettext("Your cart is about to expire. If you want to continue, please click here:"))
+                } else {
+                    $("#cart-deadline").text(
+                        cart._renewed_message + " " +
+                        ngettext(
+                            "The items in your cart are reserved for you for one minute.",
+                            "The items in your cart are reserved for you for {num} minutes.",
+                            diff_minutes
+                        ).replace(/\{num\}/g, diff_minutes)
+                    );
+                }
+                cart._prev_diff_minutes = diff_minutes;
+            }
+
             $("#cart-deadline-short").text(
                 pad(diff_minutes.toString(), 2) + ':' + pad(diff_seconds.toString(), 2)
             );
+
+            cart._renewed_message = "";
+            cart._deadline_timeout = window.setTimeout(cart.draw_deadline, 500);
+        }
+        var already_expired = diff_total_seconds <= 0;
+        var can_extend_cart = diff_minutes < 3 && (already_expired || cart._deadline < cart._max_extend);
+        $("#cart-extend-button").toggle(can_extend_cart);
+        if (can_extend_cart && diff_total_seconds < 45) {
+            if (!cart._expiry_notified) cart.show_expiry_notification();
+            $("#dialog-cart-extend-description").text(already_expired
+                ? gettext("Your cart has expired. If you want to continue, please click here:")
+                : gettext("Your cart is about to expire. If you want to continue, please click here:"));
         }
-        $("#cart-extend-button").toggle(diff_minutes < 3);
     },
 
     init: function () {
         "use strict";
-        cart._deadline = moment($("#cart-deadline").attr("data-expires"));
-        cart._deadline_interval = window.setInterval(cart.draw_deadline, 500);
         cart._calc_offset();
+        cart.set_deadline(
+            $("#cart-deadline").attr("data-expires"),
+            $("#cart-deadline").attr("data-max-expiry-extend")
+        );
+    },
+
+    set_deadline: function (expiry, max_extend, renewed_message) {
+        "use strict";
+        cart._expiry_notified = false;
+        cart._deadline = moment(expiry);
+        if (cart._deadline_timeout) {
+            window.clearTimeout(cart._deadline_timeout);
+        }
+        cart._deadline_timeout = null;
+        cart._max_extend = moment(max_extend);
+        cart._renewed_message = renewed_message || "";
         cart.draw_deadline();
     }
 };
@@ -74,6 +118,22 @@ $(function () {
         cart.init();
     }
 
+    $("#cart-extend-form").on("pretix:async-task-success", function(e, data) {
+        if (data.success) {
+            cart.set_deadline(data.expiry, data.max_expiry_extend, data.message);
+            var cart_panel_heading = $(this).closest(".panel").find(".panel-heading").get(0);
+            if (cart_panel_heading) {
+                cart_panel_heading.focus();
+            }
+        } else {
+            alert(data.message);
+        }
+    });
+
+    $("#dialog-cart-extend form").submit(function() {
+        $("#cart-extend-form").submit();
+    });
+
     $(".toggle-container").each(function() {
         var summary = $(".toggle-summary", this);
         var content = $("> :not(.toggle-summary)", this);
diff --git a/src/pretix/static/pretixpresale/js/ui/main.js b/src/pretix/static/pretixpresale/js/ui/main.js
index 5476d94f8..fd52ab84f 100644
--- a/src/pretix/static/pretixpresale/js/ui/main.js
+++ b/src/pretix/static/pretixpresale/js/ui/main.js
@@ -407,8 +407,6 @@ $(function () {
         $("#voucher-toggle").slideUp();
     });
 
-    $("#ajaxerr").on("click", ".ajaxerr-close", ajaxErrDialog.hide);
-
     // Handlers for "Copy answers from above" buttons
     $(".js-copy-answers").click(function (e) {
         e.preventDefault();
diff --git a/src/pretix/static/pretixpresale/js/ui/sso.js b/src/pretix/static/pretixpresale/js/ui/sso.js
index f8fd40c9d..0a096abb1 100644
--- a/src/pretix/static/pretixpresale/js/ui/sso.js
+++ b/src/pretix/static/pretixpresale/js/ui/sso.js
@@ -4,8 +4,6 @@ $(function () {
     var popup_window = null
     var popup_check_interval = null
 
-    $("#popupmodal").removeAttr("hidden");
-
     $("a[data-open-in-popup-window]").on("click", function (e) {
         e.preventDefault()
 
@@ -22,11 +20,13 @@ $(function () {
             "presale-popup",
             "scrollbars=yes,resizable=yes,status=yes,location=yes,toolbar=no,menubar=no,width=940,height=620,left=50,top=50"
         )
-        $("body").addClass("has-popup")
+        $("body").addClass("has-popup has-modal-dialog")
+        $("#popupmodal").removeAttr("hidden");
 
         popup_check_interval = window.setInterval(function () {
             if (popup_window.closed) {
-                $("body").removeClass("has-popup")
+                $("body").removeClass("has-popup has-modal-dialog")
+                $("#popupmodal").attr("hidden", true);
                 window.clearInterval(popup_check_interval)
             }
         }, 250)
diff --git a/src/pretix/static/pretixpresale/scss/main.scss b/src/pretix/static/pretixpresale/scss/main.scss
index c648922e3..fccf300d4 100644
--- a/src/pretix/static/pretixpresale/scss/main.scss
+++ b/src/pretix/static/pretixpresale/scss/main.scss
@@ -44,6 +44,7 @@ $headings-small-color: $text-muted;
 
 @import "../../bootstrap/scss/_bootstrap_reduced.scss";
 @import "../../pretixbase/scss/_theme.scss";
+@import "../../pretixbase/scss/_dialogs.scss";
 @import "../../lightbox/css/lightbox.scss";
 @import "../../cropper/cropper.scss";
 @import "../../datetimepicker/_bootstrap-datetimepicker.scss";
@@ -113,7 +114,7 @@ pre {
 h1, h2, h3, h4, h5, h6, p, li {
     a:not(.btn) {
         text-decoration: underline;
-    }    
+    }
 }
 
 a.no-underline:link, nav li a:link {
@@ -277,119 +278,12 @@ a:hover .panel-primary > .panel-heading {
   margin-right: auto;
 }
 
-body.loading .container {
-    -webkit-filter: blur(2px);
-    -moz-filter: blur(2px);
-    -ms-filter: blur(2px);
-    -o-filter: blur(2px);
-    filter: blur(2px);
-}
-
 .big-rotating-icon {
     -webkit-animation: fa-spin 8s infinite linear;
     animation: fa-spin 8s infinite linear;
     font-size: 120px;
     color: $brand-primary;
 }
-#loadingmodal, #ajaxerr, #popupmodal {
-    position: fixed;
-    top: 0;
-    left: 0;
-    width: 100vw;
-    height: 100vh;
-    background: rgba(255, 255, 255, .7);
-    opacity: 0;
-    z-index: 900000;
-    visibility: hidden;
-    padding: 10px;
-
-    .big-icon {
-        margin-top: 50px;
-        font-size: 200px;
-        color: $brand-primary;
-    }
-    &#popupmodal .big-icon {
-        margin-top: 10px;
-        font-size: 100px;
-        color: $brand-primary;
-    }
-
-    .modal-card {
-        margin: 50px auto 0;
-        width: 90%;
-        max-width: 600px;
-        max-height: calc(100vh - 100px);
-        overflow-y: auto;
-        background: white;
-        border-radius: $border-radius-large;
-        box-shadow: 0 7px 14px 0 rgba(78, 50, 92, 0.1),0 3px 6px 0 rgba(0,0,0,.07);
-        padding: 20px;
-        min-height: 160px;
-
-        .modal-card-icon {
-            float: left;
-            width: 150px;
-            text-align: center;
-        }
-        .modal-card-content {
-            margin-left: 160px;
-            text-align: left;
-            h3 {
-                margin-top: 0;
-            }
-        }
-    }
-
-    &#cookie-consent-modal {
-        background: rgba(255, 255, 255, .5);
-        opacity: 1;
-        visibility: visible;
-        display: none;
-        .modal-card-content {
-            margin-left: 0;
-        }
-        details {
-            & > summary {
-                list-style: none;
-            }
-            & > summary::-webkit-details-marker,
-            & > summary::marker {
-                display: none;
-            }
-            margin-bottom: 10px;
-        }
-    }
-}
-@media (max-width: 700px) {
-    #loadingmodal, #ajaxerr, #popupmodal {
-        .modal-card {
-            margin: 25px auto 0;
-            max-height: calc(100vh - 50px - 20px);
-            .modal-card-icon {
-                float: none;
-                width: 100%;
-            }
-            .modal-card-content {
-                text-align: center;
-                margin-left: 0;
-                margin-right: 0;
-                margin-top: 10px;
-            }
-        }
-    }
-}
-
-#ajaxerr {
-    background: rgba(236, 236, 236, .9);
-}
-
-.loading #loadingmodal, .ajaxerr #ajaxerr, .has-popup #popupmodal {
-    opacity: 1;
-    visibility: visible;
-    transition: opacity .5s ease-in-out;
-    -moz-transition: opacity .5s ease-in-out;
-    -webkit-transition: opacity .5s ease-in-out;
-}
 
 .typo-alert span[data-typosuggest] {
     text-decoration: underline;