diff --git a/app/lib/features/geckoview/features/browser/domain/services/browser_addon.dart b/app/lib/features/geckoview/features/browser/domain/services/browser_addon.dart
index d060c68a..c044f3c4 100644
--- a/app/lib/features/geckoview/features/browser/domain/services/browser_addon.dart
+++ b/app/lib/features/geckoview/features/browser/domain/services/browser_addon.dart
@@ -18,7 +18,9 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 import 'dart:convert';
+import 'dart:io';
 
+import 'package:flutter_mozilla_components/flutter_mozilla_components.dart';
 import 'package:http/http.dart' as http;
 import 'package:riverpod_annotation/riverpod_annotation.dart';
 import 'package:weblibre/core/logger.dart';
@@ -26,6 +28,8 @@ import 'package:weblibre/features/geckoview/domain/providers.dart';
 
 part 'browser_addon.g.dart';
 
+const _signatureRequiredPref = 'xpinstall.signatures.required';
+
 @Riverpod(keepAlive: true)
 class BrowserAddonService extends _$BrowserAddonService {
   Future<Uri> getAddonXpiUrl(String guid) async {
@@ -64,6 +68,49 @@ class BrowserAddonService extends _$BrowserAddonService {
     }
   }
 
+  Future<bool> installFromFile(
+    String filePath, {
+    bool allowUnsigned = false,
+  }) async {
+    final prefService = GeckoPrefService();
+
+    try {
+      // Validate file exists and has .xpi extension
+      final file = File(filePath);
+      if (!file.existsSync()) {
+        throw Exception('File does not exist: $filePath');
+      }
+
+      final extension = filePath.toLowerCase();
+      if (!extension.endsWith('.xpi')) {
+        throw Exception('Invalid file type. Expected .xpi file');
+      }
+
+      // Temporarily disable signature requirement if user allows unsigned
+      if (allowUnsigned) {
+        await prefService.applyPrefs({_signatureRequiredPref: false});
+      }
+
+      try {
+        // Create file:// URI and install
+        final fileUri = Uri.file(filePath);
+        if (!ref.mounted) return false;
+
+        await ref.read(addonServiceProvider).installAddon(fileUri);
+
+        return true;
+      } finally {
+        // Always restore signature requirement
+        if (allowUnsigned) {
+          await prefService.applyPrefs({_signatureRequiredPref: true});
+        }
+      }
+    } catch (e, s) {
+      logger.e('Failed installing from file: $filePath', error: e, stackTrace: s);
+      rethrow;
+    }
+  }
+
   @override
   void build() {}
 }
diff --git a/app/lib/features/geckoview/features/browser/domain/services/browser_addon.g.dart b/app/lib/features/geckoview/features/browser/domain/services/browser_addon.g.dart
index ee362cd9..879d2a97 100644
--- a/app/lib/features/geckoview/features/browser/domain/services/browser_addon.g.dart
+++ b/app/lib/features/geckoview/features/browser/domain/services/browser_addon.g.dart
@@ -42,7 +42,7 @@ final class BrowserAddonServiceProvider
 }
 
 String _$browserAddonServiceHash() =>
-    r'e7a94f86edc900339518ea0cc0e6fdbd9eccd065';
+    r'1485fd056ce32e142e342e920affb82a5c77a370';
 
 abstract class _$BrowserAddonService extends $Notifier<void> {
   void build();
diff --git a/app/lib/features/geckoview/features/browser/presentation/dialogs/install_local_addon_dialog.dart b/app/lib/features/geckoview/features/browser/presentation/dialogs/install_local_addon_dialog.dart
new file mode 100644
index 00000000..feee1790
--- /dev/null
+++ b/app/lib/features/geckoview/features/browser/presentation/dialogs/install_local_addon_dialog.dart
@@ -0,0 +1,239 @@
+/*
+ * Copyright (c) 2024-2025 Fabian Freund.
+ *
+ * This file is part of WebLibre
+ * (see https://weblibre.eu).
+ *
+ * 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, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * 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 <http://www.gnu.org/licenses/>.
+ */
+import 'package:file_picker/file_picker.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_hooks/flutter_hooks.dart';
+import 'package:go_router/go_router.dart';
+import 'package:hooks_riverpod/hooks_riverpod.dart';
+import 'package:path/path.dart' as p;
+import 'package:weblibre/features/geckoview/features/browser/domain/services/browser_addon.dart';
+
+Future<bool?> showInstallLocalAddonDialog(BuildContext context) {
+  return showModalBottomSheet<bool?>(
+    context: context,
+    isScrollControlled: true,
+    builder: (context) => const _InstallLocalAddonSheet(),
+  );
+}
+
+class _InstallLocalAddonSheet extends HookConsumerWidget {
+  const _InstallLocalAddonSheet();
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final selectedFile = useState<String?>(null);
+    final allowUnsigned = useState(false);
+    final isInstalling = useState(false);
+    final errorMessage = useState<String?>(null);
+
+    Future<void> pickFile() async {
+      try {
+        final result = await FilePicker.platform.pickFiles();
+
+        if (result != null && result.files.isNotEmpty) {
+          final path = result.files.single.path;
+          if (path != null) {
+            final extension = p.extension(path).toLowerCase();
+            if (extension == '.xpi') {
+              selectedFile.value = path;
+              errorMessage.value = null;
+            } else {
+              errorMessage.value = 'Please select an .xpi file';
+            }
+          }
+        }
+      } catch (e) {
+        errorMessage.value = 'Failed to pick file: $e';
+      }
+    }
+
+    Future<void> install() async {
+      if (selectedFile.value == null) return;
+
+      isInstalling.value = true;
+      errorMessage.value = null;
+
+      try {
+        await ref
+            .read(browserAddonServiceProvider.notifier)
+            .installFromFile(
+              selectedFile.value!,
+              allowUnsigned: allowUnsigned.value,
+            );
+
+        if (context.mounted) {
+          ScaffoldMessenger.of(context).showSnackBar(
+            const SnackBar(content: Text('Extension installed successfully')),
+          );
+          context.pop(true);
+        }
+      } catch (e) {
+        final errorString = e.toString();
+        if (errorString.contains('NotSigned') ||
+            errorString.contains('SIGNEDSTATE')) {
+          errorMessage.value =
+              'This extension is not signed by Mozilla. Enable "Allow unsigned extensions" to install it.';
+        } else {
+          errorMessage.value = 'Installation failed: $errorString';
+        }
+      } finally {
+        isInstalling.value = false;
+      }
+    }
+
+    final fileName = selectedFile.value != null
+        ? p.basename(selectedFile.value!)
+        : 'No file selected';
+
+    return SafeArea(
+      child: Padding(
+        padding: EdgeInsets.only(
+          left: 16,
+          right: 16,
+          top: 16,
+          bottom: MediaQuery.of(context).viewInsets.bottom + 16,
+        ),
+        child: Column(
+          mainAxisSize: MainAxisSize.min,
+          crossAxisAlignment: CrossAxisAlignment.stretch,
+          children: [
+            Text(
+              'Install Extension from File',
+              style: Theme.of(context).textTheme.titleLarge,
+            ),
+            const SizedBox(height: 16),
+            OutlinedButton.icon(
+              onPressed: isInstalling.value ? null : pickFile,
+              icon: const Icon(Icons.folder_open),
+              label: const Text('Select XPI File'),
+            ),
+            const SizedBox(height: 8),
+            Container(
+              padding: const EdgeInsets.all(12),
+              decoration: BoxDecoration(
+                color: Theme.of(context).colorScheme.surfaceContainerHighest,
+                borderRadius: BorderRadius.circular(8),
+              ),
+              child: Row(
+                children: [
+                  Icon(
+                    selectedFile.value != null
+                        ? Icons.extension
+                        : Icons.file_present_outlined,
+                    size: 20,
+                  ),
+                  const SizedBox(width: 8),
+                  Expanded(
+                    child: Text(
+                      fileName,
+                      style: TextStyle(
+                        color: selectedFile.value != null
+                            ? null
+                            : Theme.of(context).colorScheme.outline,
+                      ),
+                      overflow: TextOverflow.ellipsis,
+                    ),
+                  ),
+                ],
+              ),
+            ),
+            const SizedBox(height: 16),
+            SwitchListTile(
+              contentPadding: EdgeInsets.zero,
+              title: const Text('Allow unsigned extensions'),
+              subtitle: const Text(
+                'Unsigned extensions have not been verified by Mozilla',
+              ),
+              value: allowUnsigned.value,
+              onChanged: isInstalling.value
+                  ? null
+                  : (value) => allowUnsigned.value = value,
+            ),
+            if (allowUnsigned.value) ...[
+              const SizedBox(height: 8),
+              Container(
+                padding: const EdgeInsets.all(12),
+                decoration: BoxDecoration(
+                  color: Theme.of(
+                    context,
+                  ).colorScheme.errorContainer.withValues(alpha: 0.5),
+                  borderRadius: BorderRadius.circular(8),
+                  border: Border.all(
+                    color: Theme.of(context).colorScheme.error,
+                  ),
+                ),
+                child: Row(
+                  children: [
+                    Icon(
+                      Icons.warning_amber,
+                      color: Theme.of(context).colorScheme.error,
+                      size: 20,
+                    ),
+                    const SizedBox(width: 8),
+                    Expanded(
+                      child: Text(
+                        'Only install unsigned extensions from sources you trust. '
+                        'They may contain malicious code.',
+                        style: TextStyle(
+                          color: Theme.of(context).colorScheme.onErrorContainer,
+                          fontSize: 12,
+                        ),
+                      ),
+                    ),
+                  ],
+                ),
+              ),
+            ],
+            if (errorMessage.value != null) ...[
+              const SizedBox(height: 8),
+              Container(
+                padding: const EdgeInsets.all(12),
+                decoration: BoxDecoration(
+                  color: Theme.of(context).colorScheme.errorContainer,
+                  borderRadius: BorderRadius.circular(8),
+                ),
+                child: Text(
+                  errorMessage.value!,
+                  style: TextStyle(
+                    color: Theme.of(context).colorScheme.onErrorContainer,
+                  ),
+                  maxLines: 10,
+                ),
+              ),
+            ],
+            const SizedBox(height: 16),
+            FilledButton(
+              onPressed: selectedFile.value == null || isInstalling.value
+                  ? null
+                  : install,
+              child: isInstalling.value
+                  ? const SizedBox(
+                      height: 20,
+                      width: 20,
+                      child: CircularProgressIndicator(strokeWidth: 2),
+                    )
+                  : const Text('Install'),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}
diff --git a/app/lib/features/settings/presentation/screens/advanced_settings.dart b/app/lib/features/settings/presentation/screens/advanced_settings.dart
index c108bd42..75f32c0f 100644
--- a/app/lib/features/settings/presentation/screens/advanced_settings.dart
+++ b/app/lib/features/settings/presentation/screens/advanced_settings.dart
@@ -29,6 +29,7 @@ import 'package:google_fonts/google_fonts.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 import 'package:weblibre/core/providers/app_state.dart';
 import 'package:weblibre/core/routing/routes.dart';
+import 'package:weblibre/features/geckoview/features/browser/presentation/dialogs/install_local_addon_dialog.dart';
 import 'package:weblibre/features/settings/presentation/controllers/save_settings.dart';
 import 'package:weblibre/features/settings/presentation/dialogs/user_agent_restart_dialog.dart';
 import 'package:weblibre/features/settings/presentation/widgets/custom_list_tile.dart';
@@ -56,6 +57,7 @@ class AdvancedSettingsScreen extends StatelessWidget {
               padding: const EdgeInsets.symmetric(horizontal: 12.0),
               children: const [
                 _ContentBehaviorSection(),
+                _ExtensionsSection(),
                 _StorageDebuggingSection(),
                 _ResetSection(),
               ],
@@ -83,6 +85,75 @@ class _ContentBehaviorSection extends StatelessWidget {
   }
 }
 
+class _ExtensionsSection extends StatelessWidget {
+  const _ExtensionsSection();
+
+  @override
+  Widget build(BuildContext context) {
+    return const Column(
+      children: [
+        SettingSection(name: 'Extensions'),
+        _InstallLocalAddonTile(),
+        _AddonCollectionTile(),
+      ],
+    );
+  }
+}
+
+class _InstallLocalAddonTile extends StatelessWidget {
+  const _InstallLocalAddonTile();
+
+  @override
+  Widget build(BuildContext context) {
+    return CustomListTile(
+      title: 'Install from File',
+      subtitle: 'Install an extension from a local .xpi file',
+      prefix: Padding(
+        padding: const EdgeInsets.only(right: 16.0),
+        child: Icon(
+          MdiIcons.puzzle,
+          size: 24,
+          color: Theme.of(context).colorScheme.onSurfaceVariant,
+        ),
+      ),
+      suffix: FilledButton.icon(
+        onPressed: () async {
+          await showInstallLocalAddonDialog(context);
+        },
+        icon: const Icon(Icons.file_open),
+        label: const Text('Install'),
+      ),
+    );
+  }
+}
+
+class _AddonCollectionTile extends StatelessWidget {
+  const _AddonCollectionTile();
+
+  @override
+  Widget build(BuildContext context) {
+    return CustomListTile(
+      title: 'Custom Collection',
+      subtitle: 'Use a custom Mozilla addon collection',
+      prefix: Padding(
+        padding: const EdgeInsets.only(right: 16.0),
+        child: Icon(
+          MdiIcons.folderMultiple,
+          size: 24,
+          color: Theme.of(context).colorScheme.onSurfaceVariant,
+        ),
+      ),
+      suffix: FilledButton.icon(
+        onPressed: () async {
+          await AddonCollectionRoute().push(context);
+        },
+        icon: const Icon(Icons.settings),
+        label: const Text('Configure'),
+      ),
+    );
+  }
+}
+
 class _StorageDebuggingSection extends StatelessWidget {
   const _StorageDebuggingSection();
 
diff --git a/packages/flutter_mozilla_components/android/src/main/kotlin/eu/weblibre/flutter_mozilla_components/api/GeckoAddonsApiImpl.kt b/packages/flutter_mozilla_components/android/src/main/kotlin/eu/weblibre/flutter_mozilla_components/api/GeckoAddonsApiImpl.kt
index b18e9353..cb302749 100644
--- a/packages/flutter_mozilla_components/android/src/main/kotlin/eu/weblibre/flutter_mozilla_components/api/GeckoAddonsApiImpl.kt
+++ b/packages/flutter_mozilla_components/android/src/main/kotlin/eu/weblibre/flutter_mozilla_components/api/GeckoAddonsApiImpl.kt
@@ -12,6 +12,7 @@ import eu.weblibre.flutter_mozilla_components.GlobalComponents
 import eu.weblibre.flutter_mozilla_components.addons.AddonsActivity
 import eu.weblibre.flutter_mozilla_components.pigeons.GeckoAddonsApi
 import eu.weblibre.flutter_mozilla_components.pigeons.WebExtensionActionType
+import mozilla.components.concept.engine.webextension.InstallationMethod
 
 class GeckoAddonsApiImpl(private val context: Context) : GeckoAddonsApi {
     private val components by lazy {
@@ -32,8 +33,15 @@ class GeckoAddonsApiImpl(private val context: Context) : GeckoAddonsApi {
     }
 
     override fun installAddon(url: String, callback: (Result<Unit>) -> Unit) {
+        val installMethod = if (url.startsWith("file://")) {
+            InstallationMethod.FROM_FILE
+        } else {
+            null
+        }
+
         components.core.addonManager.installAddon(
             url = url,
+            installationMethod = installMethod,
             onSuccess = { _ ->
                 callback(Result.success(Unit))
             },