feat: switch default search engine to Brave Search (#26356)

## **Description**

The MetaMask mobile in-app browser currently defaults to Google search,
which shows ads that can lead users to fake/scam websites. This PR
switches the default search engine to Brave Search, providing a
privacy-focused, ad-free search experience that better protects users.

**Changes:**
- Updated `DEFAULT_SEARCH_ENGINE` constant from `'Google'` to `'Brave'`
- Added Brave Search URL (`https://search.brave.com/search?q=`) and
refactored the if/else chain to a module-scoped lookup map
(`SEARCH_ENGINE_URLS`) for cleaner extensibility and to avoid
re-allocation on every call
- Added `'Brave Search'` option to the search engine picker in General
Settings
- Added Redux persist migration (121) to automatically switch all
existing users to Brave, following the same pattern as migration 58
- Updated `processUrlForBrowser` default parameter to use
`AppConstants.DEFAULT_SEARCH_ENGINE` instead of hardcoded `'Google'`
- Updated `SitesSearchFooter` to use the shared `SEARCH_ENGINE_URLS` map
so the "Search for ... on {engine}" label and URL correctly reflect the
selected engine (previously hardcoded to Google/DuckDuckGo only)
- Fallback for unknown search engine values now uses
`AppConstants.DEFAULT_SEARCH_ENGINE` (Brave) instead of hardcoded Google

## **Changelog**

CHANGELOG entry: Changed the default search engine to Brave Search for a
privacy-focused, ad-free browsing experience

## **Related issues**

Fixes:

## **Manual testing steps**

```gherkin
Feature: Brave Search as default search engine

  Scenario: New user searches in the in-app browser
    Given the user has freshly installed the app

    When user types a search keyword in the browser URL bar
    Then the search results are served by Brave Search (search.brave.com)

  Scenario: Existing user is migrated to Brave Search
    Given the user previously had Google or DuckDuckGo as their search engine

    When the user updates the app and launches it
    Then the search engine setting is automatically changed to Brave
    And searches in the in-app browser use Brave Search

  Scenario: Search footer label reflects selected engine
    Given the user is typing a keyword in the browser URL bar

    When the autocomplete dropdown appears
    Then the footer shows "Search for {keyword} on Brave" (not Google)
    And tapping it navigates to search.brave.com

  Scenario: User can still select other search engines
    Given the user is on Settings > General

    When user opens the Search Engine picker
    Then Google, DuckDuckGo, and Brave Search are all available options
    And the user can switch between them
    And the search footer label updates to match the selected engine
```

## **Screenshots/Recordings**

### **Before**

<!-- [screenshots/recordings] -->

### **After**

<!-- [screenshots/recordings] -->

## **Pre-merge author checklist**

- [x] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask Mobile
Coding
Standards](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/CODING_GUIDELINES.md).
- [x] I've completed the PR template to the best of my ability
- [x] I've included tests if applicable
- [x] I've documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [ ] I've applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Medium Risk**
> Changes core browser URL processing and the default search engine,
plus a state migration that mutates persisted user settings; mistakes
could send users to wrong destinations or override preferences
unexpectedly.
> 
> **Overview**
> **Switches the in-app browser default search engine from Google to
Brave.** This updates `AppConstants.DEFAULT_SEARCH_ENGINE`, adds Brave
to the General Settings search engine picker, and centralizes engine
base URLs in `SEARCH_ENGINE_URLS`.
> 
> Search URL generation is refactored to use the shared lookup (with
fallback to the default) in both `processUrlForBrowser` and
`SitesSearchFooter`, and the footer testID/text are renamed from
Google-specific to a generic `trending-search-footer-search-link`.
> 
> Adds migration `126` to move persisted `settings.searchEngine` from
`Google` to `Brave` for existing users, and updates unit/integration/e2e
tests and selectors to match the new engine + testIDs.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
471a8dd. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: AugmentedMode

app/components/UI/Sites/components/SitesSearchFooter/SitesSearchFooter.test.tsx

@@ -28,7 +28,7 @@ describe('SitesSearchFooter', () => {
     } as unknown as jest.Mocked<NavigationProp<ParamListBase>>;
 
     (useNavigation as jest.Mock).mockReturnValue(mockNavigation);
-    (useSelector as jest.Mock).mockReturnValue('Google');
+    (useSelector as jest.Mock).mockReturnValue('Brave');
     dateNowSpy = jest.spyOn(Date, 'now').mockReturnValue(1234567890);
   });
 
@@ -41,17 +41,17 @@ describe('SitesSearchFooter', () => {
     it('returns null when searchQuery is empty', () => {
       const { queryByTestId } = render(<SitesSearchFooter searchQuery="" />);
 
-      expect(queryByTestId('trending-search-footer-google-link')).toBeNull();
+      expect(queryByTestId('trending-search-footer-search-link')).toBeNull();
       expect(queryByTestId('trending-search-footer-url-link')).toBeNull();
     });
 
-    it('renders Google search link when query is provided', () => {
+    it('renders search engine link when query is provided', () => {
       const { getByTestId } = render(
         <SitesSearchFooter searchQuery="ethereum" />,
       );
 
       expect(
-        getByTestId('trending-search-footer-google-link'),
+        getByTestId('trending-search-footer-search-link'),
       ).toBeOnTheScreen();
     });
 
@@ -62,7 +62,7 @@ describe('SitesSearchFooter', () => {
 
       expect(getByTestId('trending-search-footer-url-link')).toBeOnTheScreen();
       expect(
-        getByTestId('trending-search-footer-google-link'),
+        getByTestId('trending-search-footer-search-link'),
       ).toBeOnTheScreen();
     });
 
@@ -73,7 +73,7 @@ describe('SitesSearchFooter', () => {
 
       expect(queryByTestId('trending-search-footer-url-link')).toBeNull();
       expect(
-        getByTestId('trending-search-footer-google-link'),
+        getByTestId('trending-search-footer-search-link'),
       ).toBeOnTheScreen();
     });
   });
@@ -161,26 +161,26 @@ describe('SitesSearchFooter', () => {
       expect(mockNavigation.navigate).toHaveBeenCalledTimes(1);
     });
 
-    it('navigates to Google search when Google link is pressed', () => {
+    it('navigates to Brave search when search link is pressed', () => {
       const { getByTestId } = render(
         <SitesSearchFooter searchQuery="ethereum" />,
       );
 
-      fireEvent.press(getByTestId('trending-search-footer-google-link'));
+      fireEvent.press(getByTestId('trending-search-footer-search-link'));
 
-      assertBrowserNavigation('https://www.google.com/search?q=ethereum');
+      assertBrowserNavigation('https://search.brave.com/search?q=ethereum');
       expect(mockNavigation.navigate).toHaveBeenCalledTimes(1);
     });
 
-    it('encodes special characters in Google search query', () => {
+    it('encodes special characters in Brave search query', () => {
       const { getByTestId } = render(
         <SitesSearchFooter searchQuery="ethereum & bitcoin" />,
       );
 
-      fireEvent.press(getByTestId('trending-search-footer-google-link'));
+      fireEvent.press(getByTestId('trending-search-footer-search-link'));
 
       assertBrowserNavigation(
-        'https://www.google.com/search?q=ethereum%20%26%20bitcoin',
+        'https://search.brave.com/search?q=ethereum%20%26%20bitcoin',
       );
     });
 
@@ -191,7 +191,7 @@ describe('SitesSearchFooter', () => {
         <SitesSearchFooter searchQuery="ethereum" />,
       );
 
-      fireEvent.press(getByTestId('trending-search-footer-google-link'));
+      fireEvent.press(getByTestId('trending-search-footer-search-link'));
 
       assertBrowserNavigation('https://duckduckgo.com/?q=ethereum');
       expect(mockNavigation.navigate).toHaveBeenCalledTimes(1);
@@ -204,7 +204,7 @@ describe('SitesSearchFooter', () => {
         <SitesSearchFooter searchQuery="ethereum & bitcoin" />,
       );
 
-      fireEvent.press(getByTestId('trending-search-footer-google-link'));
+      fireEvent.press(getByTestId('trending-search-footer-search-link'));
 
       assertBrowserNavigation(
         'https://duckduckgo.com/?q=ethereum%20%26%20bitcoin',
@@ -213,13 +213,13 @@ describe('SitesSearchFooter', () => {
   });
 
   describe('text display', () => {
-    it('displays search query in Google search link', () => {
+    it('displays search query in Brave search link', () => {
       const { getByText } = render(
         <SitesSearchFooter searchQuery="ethereum" />,
       );
 
       expect(getByText('ethereum')).toBeOnTheScreen();
-      expect(getByText(/on Google/)).toBeOnTheScreen();
+      expect(getByText(/on Brave/)).toBeOnTheScreen();
     });
 
     it('displays search query in DuckDuckGo search link when DuckDuckGo is selected', () => {
@@ -250,7 +250,7 @@ describe('SitesSearchFooter', () => {
 
       // Component trims or handles spaces, but doesn't return null
       expect(
-        queryByTestId('trending-search-footer-google-link'),
+        queryByTestId('trending-search-footer-search-link'),
       ).toBeOnTheScreen();
     });
 
@@ -276,7 +276,7 @@ describe('SitesSearchFooter', () => {
       );
 
       expect(
-        getByTestId('trending-search-footer-google-link'),
+        getByTestId('trending-search-footer-search-link'),
       ).toBeOnTheScreen();
     });
 
@@ -286,7 +286,7 @@ describe('SitesSearchFooter', () => {
       );
 
       expect(
-        getByTestId('trending-search-footer-google-link'),
+        getByTestId('trending-search-footer-search-link'),
       ).toBeOnTheScreen();
       expect(getByText('ethereum 🚀')).toBeOnTheScreen();
     });

app/components/UI/Sites/components/SitesSearchFooter/SitesSearchFooter.tsx

@@ -14,6 +14,8 @@ import { useNavigation } from '@react-navigation/native';
 import { useSelector } from 'react-redux';
 import Routes from '../../../../../constants/navigation/Routes';
 import { selectSearchEngine } from '../../../../../reducers/browser/selectors';
+import { SEARCH_ENGINE_URLS, SearchEngine } from '../../../../../util/browser';
+import AppConstants from '../../../../../core/AppConstants';
 
 export interface SitesSearchFooterProps {
   searchQuery: string;
@@ -72,13 +74,16 @@ const SitesSearchFooter: React.FC<SitesSearchFooterProps> = ({
 
   const isUrl = looksLikeUrl(searchQuery.toLowerCase());
 
+  const engineKey = searchEngine ?? AppConstants.DEFAULT_SEARCH_ENGINE;
+  const resolvedEngine: SearchEngine = SEARCH_ENGINE_URLS[
+    engineKey as SearchEngine
+  ]
+    ? (engineKey as SearchEngine)
+    : AppConstants.DEFAULT_SEARCH_ENGINE;
   const searchUrl =
-    searchEngine === 'DuckDuckGo'
-      ? `https://duckduckgo.com/?q=${encodeURIComponent(searchQuery)}`
-      : `https://www.google.com/search?q=${encodeURIComponent(searchQuery)}`;
+    SEARCH_ENGINE_URLS[resolvedEngine] + encodeURIComponent(searchQuery);
 
-  const searchEngineLabel =
-    searchEngine === 'DuckDuckGo' ? 'DuckDuckGo' : 'Google';
+  const searchEngineLabel = resolvedEngine;
 
   return (
     <Box style={containerStyle}>
@@ -110,7 +115,7 @@ const SitesSearchFooter: React.FC<SitesSearchFooterProps> = ({
       <TouchableOpacity
         style={tw.style('flex-row items-center py-4')}
         onPress={() => handlePress(searchUrl)}
-        testID="trending-search-footer-google-link"
+        testID="trending-search-footer-search-link"
       >
         <Box twClassName="flex-1 flex-row items-center">
           <Text

app/components/UI/UrlAutocomplete/index.test.tsx

@@ -577,10 +577,10 @@ describe('UrlAutocomplete', () => {
 
       // Assert
       expect(
-        await screen.findByTestId('trending-search-footer-google-link', {
+        await screen.findByTestId('trending-search-footer-search-link', {
           includeHiddenElements: true,
         }),
-      ).toHaveTextContent('Search for "MetaMask Test Dapp" on Google');
+      ).toHaveTextContent('Search for "MetaMask Test Dapp" on Brave');
     });
 
     it('transforms and displays token search results', async () => {

app/components/Views/Settings/GeneralSettings/index.js

@@ -259,6 +259,7 @@ class Settings extends PureComponent {
     this.searchEngineOptions = [
       { value: 'Google', label: 'Google', key: 'Google' },
       { value: 'DuckDuckGo', label: 'DuckDuckGo', key: 'DuckDuckGo' },
+      { value: 'Brave', label: 'Brave', key: 'Brave' },
     ];
     this.primaryCurrencyOptions = [
       {

app/core/AppConstants.ts

@@ -16,7 +16,7 @@ export default {
   IS_DEV: process.env?.NODE_ENV === DEVELOPMENT,
   METAMASK_BUILD_TYPE: process.env.METAMASK_BUILD_TYPE,
   DEFAULT_LOCK_TIMEOUT: 30000,
-  DEFAULT_SEARCH_ENGINE: 'Google',
+  DEFAULT_SEARCH_ENGINE: 'Brave',
   TX_CHECK_BACKGROUND_FREQUENCY: 30000,
   IPFS_OVERRIDE_PARAM: 'mm_override',
   IPFS_DEFAULT_GATEWAY_URL: 'https://dweb.link/ipfs/',

app/store/migrations/126.test.ts

@@ -0,0 +1,121 @@
+import migrate from './126';
+import { merge } from 'lodash';
+import { captureException } from '@sentry/react-native';
+import initialRootState from '../../util/test/initial-root-state';
+import mockedEngine from '../../core/__mocks__/MockedEngine';
+
+jest.mock('@sentry/react-native', () => ({
+  captureException: jest.fn(),
+}));
+const mockedCaptureException = jest.mocked(captureException);
+
+jest.mock('../../core/Engine', () => ({
+  init: () => mockedEngine.init(),
+}));
+
+describe('Migration #126 - Update default search engine to Brave', () => {
+  beforeEach(() => {
+    jest.restoreAllMocks();
+    jest.resetAllMocks();
+  });
+
+  const invalidStates = [
+    {
+      state: null,
+      errorMessage: "FATAL ERROR: Migration 126: Invalid state error: 'object'",
+      scenario: 'state is invalid',
+    },
+    {
+      state: merge({}, initialRootState, {
+        engine: null,
+      }),
+      errorMessage:
+        "FATAL ERROR: Migration 126: Invalid engine state error: 'object'",
+      scenario: 'engine state is invalid',
+    },
+    {
+      state: merge({}, initialRootState, {
+        engine: {
+          backgroundState: null,
+        },
+      }),
+      errorMessage:
+        "FATAL ERROR: Migration 126: Invalid engine backgroundState error: 'object'",
+      scenario: 'backgroundState is invalid',
+    },
+    {
+      state: merge({}, initialRootState, {
+        engine: {
+          backgroundState: {},
+        },
+        settings: null,
+      }),
+      errorMessage:
+        "FATAL ERROR: Migration 126: Invalid Settings state error: 'object'",
+      scenario: 'Settings object is invalid',
+    },
+  ];
+
+  for (const { errorMessage, scenario, state } of invalidStates) {
+    it(`captures exception if ${scenario}`, async () => {
+      const newState = await migrate(state);
+
+      expect(newState).toStrictEqual(state);
+      expect(mockedCaptureException).toHaveBeenCalledWith(expect.any(Error));
+      expect(mockedCaptureException.mock.calls[0][0].message).toBe(
+        errorMessage,
+      );
+    });
+  }
+
+  it('updates the search engine from Google to Brave', async () => {
+    const oldState = {
+      engine: {
+        backgroundState: {},
+      },
+      settings: {
+        searchEngine: 'Google',
+      },
+    };
+
+    const expectedState = {
+      engine: {
+        backgroundState: {},
+      },
+      settings: {
+        searchEngine: 'Brave',
+      },
+    };
+
+    const migratedState = await migrate(oldState);
+    expect(migratedState).toStrictEqual(expectedState);
+  });
+
+  it('does not change the search engine if it is already DuckDuckGo', async () => {
+    const oldState = {
+      engine: {
+        backgroundState: {},
+      },
+      settings: {
+        searchEngine: 'DuckDuckGo',
+      },
+    };
+
+    const migratedState = await migrate(oldState);
+    expect(migratedState).toStrictEqual(oldState);
+  });
+
+  it('does not change the search engine if it is already Brave', async () => {
+    const oldState = {
+      engine: {
+        backgroundState: {},
+      },
+      settings: {
+        searchEngine: 'Brave',
+      },
+    };
+
+    const migratedState = await migrate(oldState);
+    expect(migratedState).toStrictEqual(oldState);
+  });
+});

app/store/migrations/126.ts

@@ -0,0 +1,33 @@
+import { captureException } from '@sentry/react-native';
+import { isObject } from '@metamask/utils';
+import { ensureValidState } from './util';
+
+/**
+ * Migration 126: Change default search engine to Brave
+ *
+ * All existing users will be migrated to 'Brave' for a privacy-focused,
+ * ad-free search experience.
+ *
+ * @param state - The persisted Redux state
+ * @returns The migrated Redux state
+ */
+export default function migrate(state: unknown) {
+  if (!ensureValidState(state, 126)) {
+    return state;
+  }
+
+  if (!isObject(state.settings)) {
+    captureException(
+      new Error(
+        `FATAL ERROR: Migration 126: Invalid Settings state error: '${typeof state.settings}'`,
+      ),
+    );
+    return state;
+  }
+
+  if (state.settings.searchEngine === 'Google') {
+    state.settings.searchEngine = 'Brave';
+  }
+
+  return state;
+}

app/store/migrations/index.ts

@@ -126,6 +126,7 @@ import migration122 from './122';
 import migration123 from './123';
 import migration124 from './124';
 import migration125 from './125';
+import migration126 from './126';
 
 // Add migrations above this line
 import { ControllerStorage } from '../persistConfig';
@@ -271,6 +272,7 @@ export const migrationList: MigrationsList = {
   123: migration123,
   124: migration124,
   125: migration125,
+  126: migration126,
 };
 
 // Enable both synchronous and asynchronous migrations