diff --git a/dwds/debug_extension_mv3/web/debug_session.dart b/dwds/debug_extension_mv3/web/debug_session.dart
index 47ac4a813..4ceac2a4e 100644
--- a/dwds/debug_extension_mv3/web/debug_session.dart
+++ b/dwds/debug_extension_mv3/web/debug_session.dart
@@ -106,26 +106,9 @@ int? get latestAppBeingDebugged =>
 
 Future<void> attachDebugger(int dartAppTabId,
     {required Trigger trigger}) async {
-  // Check if a debugger is already attached:
-  final existingDebuggerLocation = _debuggerLocation(dartAppTabId);
-  if (existingDebuggerLocation != null) {
-    return _showWarningNotification(
-      'Already debugging in ${existingDebuggerLocation.displayName}.',
-    );
-  }
-  // Determine if there are multiple apps in the tab:
-  final multipleApps = await fetchStorageObject<String>(
-    type: StorageObject.multipleAppsDetected,
-    tabId: dartAppTabId,
-  );
-  if (multipleApps != null) {
-    return _showWarningNotification(
-      'Dart debugging is not supported in a multi-app environment.',
-    );
-  }
-  // Verify that the user is authenticated:
-  final isAuthenticated = await _authenticateUser(dartAppTabId);
-  if (!isAuthenticated) return;
+  // Validate that the tab can be debugged:
+  final tabIsDebuggable = await _validateTabIsDebuggable(dartAppTabId);
+  if (!tabIsDebuggable) return;
 
   _tabIdToTrigger[dartAppTabId] = trigger;
   _registerDebugEventListeners();
@@ -177,6 +160,40 @@ Future<void> clearStaleDebugSession(int tabId) async {
   }
 }
 
+Future<bool> _validateTabIsDebuggable(int dartAppTabId) async {
+  // Check if a debugger is already attached:
+  final existingDebuggerLocation = _debuggerLocation(dartAppTabId);
+  if (existingDebuggerLocation != null) {
+    await _showWarningNotification(
+      'Already debugging in ${existingDebuggerLocation.displayName}.',
+    );
+    return false;
+  }
+  // Determine if this is a Dart app:
+  final debugInfo = await fetchStorageObject<DebugInfo>(
+    type: StorageObject.debugInfo,
+    tabId: dartAppTabId,
+  );
+  if (debugInfo == null) {
+    await _showWarningNotification('Not a Dart app.');
+    return false;
+  }
+  // Determine if there are multiple apps in the tab:
+  final multipleApps = await fetchStorageObject<String>(
+    type: StorageObject.multipleAppsDetected,
+    tabId: dartAppTabId,
+  );
+  if (multipleApps != null) {
+    await _showWarningNotification(
+      'Dart debugging is not supported in a multi-app environment.',
+    );
+    return false;
+  }
+  // Verify that the user is authenticated:
+  final isAuthenticated = await _authenticateUser(dartAppTabId);
+  return isAuthenticated;
+}
+
 void _registerDebugEventListeners() {
   chrome.debugger.onEvent.addListener(allowInterop(_onDebuggerEvent));
   chrome.debugger.onDetach.addListener(allowInterop((source, _) async {
@@ -548,7 +565,7 @@ Future<bool> _authenticateUser(int tabId) async {
   );
   final authUrl = debugInfo?.authUrl;
   if (authUrl == null) {
-    _showWarningNotification('Cannot authenticate user.');
+    await _showWarningNotification('Cannot authenticate user.');
     return false;
   }
   final isAuthenticated = await _sendAuthRequest(authUrl);
@@ -582,7 +599,8 @@ Future<bool> _sendAuthRequest(String authUrl) async {
   return responseBody.contains('Dart Debug Authentication Success!');
 }
 
-void _showWarningNotification(String message) {
+Future<bool> _showWarningNotification(String message) {
+  final completer = Completer<bool>();
   chrome.notifications.create(
     /*notificationId*/ null,
     NotificationOptions(
@@ -591,8 +609,11 @@ void _showWarningNotification(String message) {
       iconUrl: 'static_assets/dart.png',
       type: 'basic',
     ),
-    /*callback*/ null,
+    allowInterop((_) {
+      completer.complete(true);
+    }),
   );
+  return completer.future;
 }
 
 DebuggerLocation? _debuggerLocation(int dartAppTabId) {
diff --git a/dwds/test/puppeteer/extension_test.dart b/dwds/test/puppeteer/extension_test.dart
index b68a3d882..9a48c0f90 100644
--- a/dwds/test/puppeteer/extension_test.dart
+++ b/dwds/test/puppeteer/extension_test.dart
@@ -373,6 +373,29 @@ void main() async {
             await devToolsTabTarget.onClose;
           });
 
+          test('Clicking extension icon for a non Dart app shows warning',
+              () async {
+            // Navigate to a page that doesn't contain a Dart app:
+            final tab = await navigateToPage(browser,
+                url: 'https://dart.dev', isNew: true);
+            // Click on the Dart Debug Extension icon:
+            await workerEvalDelay();
+            await clickOnExtensionIcon(
+              worker: worker,
+              backgroundPage: backgroundPage,
+            );
+            // There should now be a warning notificiation:
+            final chromeNotifications = await evaluate(
+              _getNotifications(),
+              worker: worker,
+              backgroundPage: backgroundPage,
+            );
+            await workerEvalDelay();
+            expect(chromeNotifications, isNotEmpty);
+            // Close the tab:
+            await tab.close();
+          });
+
           test('Refreshing the Dart app does not open a new Dart DevTools',
               () async {
             final appUrl = context.appUrl;
diff --git a/dwds/test/puppeteer/test_images/chromeDevTools_externalBuild.png b/dwds/test/puppeteer/test_images/chromeDevTools_externalBuild.png
index 6372516fe..0de722768 100644
Binary files a/dwds/test/puppeteer/test_images/chromeDevTools_externalBuild.png and b/dwds/test/puppeteer/test_images/chromeDevTools_externalBuild.png differ
diff --git a/dwds/test/puppeteer/test_images/debuggerPanelDisconnected_flutterApp.png b/dwds/test/puppeteer/test_images/debuggerPanelDisconnected_flutterApp.png
index c8040bfe3..96ac4caa6 100644
Binary files a/dwds/test/puppeteer/test_images/debuggerPanelDisconnected_flutterApp.png and b/dwds/test/puppeteer/test_images/debuggerPanelDisconnected_flutterApp.png differ
diff --git a/dwds/test/puppeteer/test_images/debuggerPanelLandingPage_dartApp.png b/dwds/test/puppeteer/test_images/debuggerPanelLandingPage_dartApp.png
index b9184f2e4..090a1c74b 100644
Binary files a/dwds/test/puppeteer/test_images/debuggerPanelLandingPage_dartApp.png and b/dwds/test/puppeteer/test_images/debuggerPanelLandingPage_dartApp.png differ
diff --git a/dwds/test/puppeteer/test_images/debuggerPanelLandingPage_flutterApp.png b/dwds/test/puppeteer/test_images/debuggerPanelLandingPage_flutterApp.png
index b9184f2e4..090a1c74b 100644
Binary files a/dwds/test/puppeteer/test_images/debuggerPanelLandingPage_flutterApp.png and b/dwds/test/puppeteer/test_images/debuggerPanelLandingPage_flutterApp.png differ
diff --git a/dwds/test/puppeteer/test_images/inspectorPanelLandingPage_flutterApp.png b/dwds/test/puppeteer/test_images/inspectorPanelLandingPage_flutterApp.png
index 6e4385451..39d8b8916 100644
Binary files a/dwds/test/puppeteer/test_images/inspectorPanelLandingPage_flutterApp.png and b/dwds/test/puppeteer/test_images/inspectorPanelLandingPage_flutterApp.png differ