diff --git a/contao/dca/tl_calendar_events.php b/contao/dca/tl_calendar_events.php
index 222d224..29fba6a 100644
--- a/contao/dca/tl_calendar_events.php
+++ b/contao/dca/tl_calendar_events.php
@@ -6,6 +6,7 @@ use Contao\CoreBundle\DataContainer\PaletteManipulator;
 use Contao\DataContainer;
 use Contao\Database;
 use Contao\StringUtil;
+use Contao\System;
 
 unset($GLOBALS['TL_DCA']['tl_calendar_events']['fields']['location']);
 unset($GLOBALS['TL_DCA']['tl_calendar_events']['fields']['address']);
@@ -30,7 +31,7 @@ $GLOBALS['TL_DCA']['tl_calendar_events']['config']['onload_callback'][] = static
             ->applyToPalette((string) $paletteName, 'tl_calendar_events');
 
         PaletteManipulator::create()
-            ->addField(['source', 'url', 'target'], 'details_legend', PaletteManipulator::POSITION_APPEND)
+            ->addField(['source', 'url'], 'details_legend', PaletteManipulator::POSITION_APPEND)
             ->addField(['termsAccepted', 'isSoldOut', 'isCanceled'], 'publish_legend', PaletteManipulator::POSITION_APPEND)
             ->applyToPalette((string) $paletteName, 'tl_calendar_events');
     }
@@ -169,6 +170,20 @@ $GLOBALS['TL_DCA']['tl_calendar_events']['fields']['termsAccepted'] = [
 if (isset($GLOBALS['TL_DCA']['tl_calendar_events']['fields']['source']) && is_array($GLOBALS['TL_DCA']['tl_calendar_events']['fields']['source'])) {
     $GLOBALS['TL_DCA']['tl_calendar_events']['fields']['source']['eval'] ??= [];
     $GLOBALS['TL_DCA']['tl_calendar_events']['fields']['source']['eval']['tl_class'] = 'w50';
+
+    // Keine Weiterleitung auf externe Seiten: Events öffnen immer die Detailseite,
+    // die externe URL (Feld "url") wird dort als Button ausgegeben.
+    $originalSourceOptionsCallback = $GLOBALS['TL_DCA']['tl_calendar_events']['fields']['source']['options_callback'] ?? null;
+
+    if (null !== $originalSourceOptionsCallback) {
+        $GLOBALS['TL_DCA']['tl_calendar_events']['fields']['source']['options_callback'] = static function (DataContainer $dc) use ($originalSourceOptionsCallback): array {
+            $options = \is_array($originalSourceOptionsCallback)
+                ? System::importStatic($originalSourceOptionsCallback[0])->{$originalSourceOptionsCallback[1]}($dc)
+                : $originalSourceOptionsCallback($dc);
+
+            return array_values(array_diff((array) $options, ['external']));
+        };
+    }
 }
 
 if (isset($GLOBALS['TL_DCA']['tl_calendar_events']['fields']['target']) && is_array($GLOBALS['TL_DCA']['tl_calendar_events']['fields']['target'])) {
@@ -179,6 +194,7 @@ if (isset($GLOBALS['TL_DCA']['tl_calendar_events']['fields']['target']) && is_ar
 if (isset($GLOBALS['TL_DCA']['tl_calendar_events']['fields']['url']) && is_array($GLOBALS['TL_DCA']['tl_calendar_events']['fields']['url'])) {
     $GLOBALS['TL_DCA']['tl_calendar_events']['fields']['url']['eval'] ??= [];
     $GLOBALS['TL_DCA']['tl_calendar_events']['fields']['url']['eval']['tl_class'] = 'clr';
+    $GLOBALS['TL_DCA']['tl_calendar_events']['fields']['url']['label'] = &$GLOBALS['TL_LANG']['tl_calendar_events']['url'];
     $GLOBALS['TL_DCA']['tl_calendar_events']['fields']['url']['eval']['mandatory'] = false;
     unset($GLOBALS['TL_DCA']['tl_calendar_events']['fields']['url']['eval']['rgxp']);
 }
diff --git a/contao/languages/de/tl_calendar_events.php b/contao/languages/de/tl_calendar_events.php
index d92ab52..5ef83c5 100644
--- a/contao/languages/de/tl_calendar_events.php
+++ b/contao/languages/de/tl_calendar_events.php
@@ -10,3 +10,4 @@ $GLOBALS['TL_LANG']['tl_calendar_events']['photographer'] = ['Urheber/Fotograf',
 $GLOBALS['TL_LANG']['tl_calendar_events']['isSoldOut'] = ['Ausverkauft', 'Diese Veranstaltung ist ausverkauft.'];
 $GLOBALS['TL_LANG']['tl_calendar_events']['isCanceled'] = ['Abgesagt', 'Diese Veranstaltung wurde abgesagt.'];
 $GLOBALS['TL_LANG']['tl_calendar_events']['termsAccepted'] = ['Nutzungsbedingungen akzeptiert', 'Die Nutzungsbedingungen wurden akzeptiert.'];
+$GLOBALS['TL_LANG']['tl_calendar_events']['url'] = ['Externer Link', 'Weiterführende Seite zur Veranstaltung (z. B. Website des Veranstalters). Wird auf der Detailseite als Button ausgegeben; Listen verlinken immer auf die Detailseite.'];
diff --git a/contao/languages/en/tl_calendar_events.php b/contao/languages/en/tl_calendar_events.php
index 61f0a11..9073260 100644
--- a/contao/languages/en/tl_calendar_events.php
+++ b/contao/languages/en/tl_calendar_events.php
@@ -10,3 +10,4 @@ $GLOBALS['TL_LANG']['tl_calendar_events']['photographer'] = ['Author/Photographe
 $GLOBALS['TL_LANG']['tl_calendar_events']['isSoldOut'] = ['Sold out', 'This event is sold out.'];
 $GLOBALS['TL_LANG']['tl_calendar_events']['isCanceled'] = ['Canceled', 'This event has been canceled.'];
 $GLOBALS['TL_LANG']['tl_calendar_events']['termsAccepted'] = ['Terms accepted', 'The terms of use have been accepted.'];
+$GLOBALS['TL_LANG']['tl_calendar_events']['url'] = ['External link', 'Further page about the event (e.g. organiser website). Shown as a button on the event detail page; lists always link to the detail page.'];
diff --git a/src/Migration/ExternalEventSourceMigration.php b/src/Migration/ExternalEventSourceMigration.php
new file mode 100644
index 0000000..851080c
--- /dev/null
+++ b/src/Migration/ExternalEventSourceMigration.php
@@ -0,0 +1,49 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Mummert\EventManagerBundle\Migration;
+
+use Contao\CoreBundle\Migration\AbstractMigration;
+use Contao\CoreBundle\Migration\MigrationResult;
+use Doctrine\DBAL\Connection;
+
+/**
+ * Events mit externer URL öffnen künftig immer die Detailseite. Die URL bleibt im
+ * Feld "url" erhalten und wird auf der Detailseite als Button ausgegeben.
+ * Stellt dafür bestehende Events von source = "external" auf "default" um.
+ */
+class ExternalEventSourceMigration extends AbstractMigration
+{
+    public function __construct(
+        private readonly Connection $connection,
+    ) {
+    }
+
+    public function getName(): string
+    {
+        return 'Eventmanager: Events mit externer URL auf Detailseite umstellen';
+    }
+
+    public function shouldRun(): bool
+    {
+        $schemaManager = $this->connection->createSchemaManager();
+
+        if (!$schemaManager->tablesExist(['tl_calendar_events'])) {
+            return false;
+        }
+
+        return (int) $this->connection->fetchOne(
+            "SELECT COUNT(*) FROM tl_calendar_events WHERE source = 'external'",
+        ) > 0;
+    }
+
+    public function run(): MigrationResult
+    {
+        $count = $this->connection->executeStatement(
+            "UPDATE tl_calendar_events SET source = 'default' WHERE source = 'external'",
+        );
+
+        return $this->createResult(true, sprintf('%d Events von externer Weiterleitung auf Detailseite umgestellt.', $count));
+    }
+}
diff --git a/src/Service/EventRepository.php b/src/Service/EventRepository.php
index 45d8f30..90f8abf 100644
--- a/src/Service/EventRepository.php
+++ b/src/Service/EventRepository.php
@@ -651,7 +651,8 @@ class EventRepository
             'teaser' => $data['teaser'] ?? null,
             'description' => $data['description'] ?? null,
             'url' => $url,
-            'source' => '' !== $url ? 'external' : 'default',
+            // Externe URL wird nur als Link-Button auf der Detailseite ausgegeben, Listen verlinken immer auf die Detailseite
+            'source' => 'default',
             'photographer' => $data['photographer'] ?? '',
             'addImage' => !empty($data['addImage']) ? 1 : 0,
             'termsAccepted' => !empty($data['termsAccepted']) ? '1' : '',