diff --git a/core/assets/scaffold/files/default.settings.php b/core/assets/scaffold/files/default.settings.php
index 5784a9c7523..ee3b49c0a8d 100644
--- a/core/assets/scaffold/files/default.settings.php
+++ b/core/assets/scaffold/files/default.settings.php
@@ -765,6 +765,49 @@ $settings['entity_update_backup'] = TRUE;
  */
 $settings['migrate_node_migrate_type_classic'] = FALSE;
 
+/**
+ * The default settings for migration sources.
+ *
+ * These settings are used as the default settings on the Credential form at
+ * /upgrade/credentials.
+ *
+ * - migrate_source_version - The version of the source database. This can be
+ *   '6' or '7'. Defaults to '7'.
+ * - migrate_source_connection - The key in the $databases array for the source
+ *   site.
+ * - migrate_file_public_path - The location of the source Drupal 6 or Drupal 7
+ *   public files. This can be a local file directory containing the source
+ *   Drupal 6 or Drupal 7 site (e.g /var/www/docroot), or the site address
+ *   (e.g http://example.com).
+ * - migrate_file_private_path - The location of the source Drupal 7 private
+ *   files. This can be a local file directory containing the source Drupal 7
+ *   site (e.g /var/www/docroot), or empty to use the same value as Public
+ *   files directory.
+ *
+ * Sample configuration for a drupal 6 source site with the source files in a
+ * local directory.
+ *
+ * @code
+ * $settings['migrate_source_version'] = '6';
+ * $settings['migrate_source_connection'] = 'migrate';
+ * $settings['migrate_file_public_path'] = '/var/www/drupal6';
+ * @endcode
+ *
+ * Sample configuration for a drupal 7 source site with public source files on
+ * the source site and the private files in a local directory.
+ *
+ * @code
+ * $settings['migrate_source_version'] = '7';
+ * $settings['migrate_source_connection'] = 'migrate';
+ * $settings['migrate_file_public_path'] = 'https://drupal7.com';
+ * $settings['migrate_file_private_path'] = '/var/www/drupal7';
+ * @endcode
+ */
+# $settings['migrate_source_connection'] = '';
+# $settings['migrate_source_version'] = '';
+# $settings['migrate_file_public_path'] = '';
+# $settings['migrate_file_private_path'] = '';
+
 /**
  * Load local development override configuration, if available.
  *
diff --git a/core/modules/migrate_drupal_ui/src/Form/CredentialForm.php b/core/modules/migrate_drupal_ui/src/Form/CredentialForm.php
index 8900a507684..87e57604bb8 100644
--- a/core/modules/migrate_drupal_ui/src/Form/CredentialForm.php
+++ b/core/modules/migrate_drupal_ui/src/Form/CredentialForm.php
@@ -5,8 +5,10 @@ namespace Drupal\migrate_drupal_ui\Form;
 use Drupal\Component\Utility\UrlHelper;
 use Drupal\Core\Config\ConfigFactoryInterface;
 use Drupal\Core\Database\Connection;
+use Drupal\Core\Database\Database;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\State\StateInterface;
+use Drupal\Core\Site\Settings;
 use Drupal\Core\TempStore\PrivateTempStoreFactory;
 use Drupal\migrate\Exception\RequirementsException;
 use Drupal\migrate\Plugin\Exception\BadPluginDefinitionException;
@@ -99,19 +101,42 @@ class CredentialForm extends MigrateUpgradeFormBase {
       '#description' => $this->t('Provide the information to access the Drupal site you want to upgrade. Files can be imported into the upgraded site as well.  See the <a href=":url">Upgrade documentation for more detailed instructions</a>.', [':url' => 'https://www.drupal.org/upgrade/migrate']),
     ];
 
+    $migrate_source_version = Settings::get('migrate_source_version') == '6' ? '6' : '7';
     $form['version'] = [
       '#type' => 'radios',
-      '#default_value' => 7,
+      '#default_value' => $migrate_source_version,
       '#title' => $this->t('Drupal version of the source site'),
       '#options' => ['6' => $this->t('Drupal 6'), '7' => $this->t('Drupal 7')],
       '#required' => TRUE,
     ];
 
+    $available_connections = array_diff(array_keys(Database::getAllConnectionInfo()), ['default']);
+    $options = array_combine($available_connections, $available_connections);
+    $migrate_source_connection = Settings::get('migrate_source_connection');
+    $preferred_connections = $migrate_source_connection
+      ? ['migrate', $migrate_source_connection]
+      : ['migrate'];
+    $default_options = array_intersect($preferred_connections, $available_connections);
+    $form['source_connection'] = [
+      '#type' => 'select',
+      '#title' => $this->t('Source connection'),
+      '#options' => $options,
+      '#default_value' => array_pop($default_options),
+      '#empty_option' => $this->t('- User defined -'),
+      '#description' => $this->t('Choose one of the keys from the $databases array or else select "User defined" and enter database credentials.'),
+      '#access' => !empty($options),
+    ];
+
     $form['database'] = [
       '#type' => 'details',
       '#title' => $this->t('Source database'),
       '#description' => $this->t('Provide credentials for the database of the Drupal site you want to upgrade.'),
       '#open' => TRUE,
+      '#states' => [
+        'visible' => [
+          ':input[name=source_connection]' => ['value' => ''],
+        ],
+      ],
     ];
 
     $form['database']['driver'] = [
@@ -119,6 +144,11 @@ class CredentialForm extends MigrateUpgradeFormBase {
       '#title' => $this->t('Database type'),
       '#required' => TRUE,
       '#default_value' => $default_driver,
+      '#states' => [
+        'required' => [
+          ':input[name=source_connection]' => ['value' => ''],
+        ],
+      ],
     ];
     if (count($drivers) == 1) {
       $form['database']['driver']['#disabled'] = TRUE;
@@ -136,6 +166,27 @@ class CredentialForm extends MigrateUpgradeFormBase {
       // for mysql and pgsql must not be required.
       $form['database']['settings'][$key]['database']['#required'] = FALSE;
       $form['database']['settings'][$key]['username']['#required'] = FALSE;
+      $form['database']['settings'][$key]['database']['#states'] = [
+        'required' => [
+          ':input[name=source_connection]' => ['value' => ''],
+          ':input[name=driver]' => ['value' => $key],
+        ],
+      ];
+      if ($key != 'sqlite') {
+        $form['database']['settings'][$key]['username']['#states'] = [
+          'required' => [
+            ':input[name=source_connection]' => ['value' => ''],
+            ':input[name=driver]' => ['value' => $key],
+          ],
+        ];
+        $form['database']['settings'][$key]['password']['#states'] = [
+          'required' => [
+            ':input[name=source_connection]' => ['value' => ''],
+            ':input[name=driver]' => ['value' => $key],
+          ],
+        ];
+      }
+
       $form['database']['settings'][$key]['#prefix'] = '<h2 class="js-hide">' . $this->t('@driver_name settings', ['@driver_name' => $driver->name()]) . '</h2>';
       $form['database']['settings'][$key]['#type'] = 'container';
       $form['database']['settings'][$key]['#tree'] = TRUE;
@@ -164,6 +215,7 @@ class CredentialForm extends MigrateUpgradeFormBase {
     $form['source']['d6_source_base_path'] = [
       '#type' => 'textfield',
       '#title' => $this->t('Document root for files'),
+      '#default_value' => Settings::get('migrate_file_public_path') ?? '',
       '#description' => $this->t('To import files from your current Drupal site, enter a local file directory containing your site (e.g. /var/www/docroot), or your site address (for example http://example.com).'),
       '#states' => [
         'visible' => [
@@ -176,6 +228,7 @@ class CredentialForm extends MigrateUpgradeFormBase {
     $form['source']['source_base_path'] = [
       '#type' => 'textfield',
       '#title' => $this->t('Document root for public files'),
+      '#default_value' => Settings::get('migrate_file_public_path') ?? '',
       '#description' => $this->t('To import public files from your current Drupal site, enter a local file directory containing your site (e.g. /var/www/docroot), or your site address (for example http://example.com).'),
       '#states' => [
         'visible' => [
@@ -188,7 +241,7 @@ class CredentialForm extends MigrateUpgradeFormBase {
     $form['source']['source_private_file_path'] = [
       '#type' => 'textfield',
       '#title' => $this->t('Document root for private files'),
-      '#default_value' => '',
+      '#default_value' => Settings::get('migrate_file_private_path') ?? '',
       '#description' => $this->t('To import private files from your current Drupal site, enter a local file directory containing your site (e.g. /var/www/docroot). Leave blank to use the same value as Public files directory.'),
       '#states' => [
         'visible' => [
@@ -205,29 +258,36 @@ class CredentialForm extends MigrateUpgradeFormBase {
    * {@inheritdoc}
    */
   public function validateForm(array &$form, FormStateInterface $form_state) {
-    // Retrieve the database driver from the form, use reflection to get the
-    // namespace, and then construct a valid database array the same as in
-    // settings.php.
-    $driver = $form_state->getValue('driver');
-    $drivers = $this->getDatabaseTypes();
-    $reflection = new \ReflectionClass($drivers[$driver]);
-    $install_namespace = $reflection->getNamespaceName();
+    $source_connection = $form_state->getValue('source_connection');
+    if ($source_connection) {
+      $info = Database::getConnectionInfo($source_connection);
+      $database = reset($info);
+    }
+    else {
+      // Retrieve the database driver from the form, use reflection to get the
+      // namespace, and then construct a valid database array the same as in
+      // settings.php.
+      $driver = $form_state->getValue('driver');
+      $drivers = $this->getDatabaseTypes();
+      $reflection = new \ReflectionClass($drivers[$driver]);
+      $install_namespace = $reflection->getNamespaceName();
 
-    $database = $form_state->getValue($driver);
-    // Cut the trailing \Install from namespace.
-    $database['namespace'] = substr($install_namespace, 0, strrpos($install_namespace, '\\'));
-    $database['driver'] = $driver;
+      $database = $form_state->getValue($driver);
+      // Cut the trailing \Install from namespace.
+      $database['namespace'] = substr($install_namespace, 0, strrpos($install_namespace, '\\'));
+      $database['driver'] = $driver;
 
-    // Validate the driver settings and just end here if we have any issues.
-    $connection = NULL;
-    $error_key = $database['driver'] . '][database';
-    if ($errors = $drivers[$driver]->validateDatabaseSettings($database)) {
-      foreach ($errors as $name => $message) {
-        $this->errors[$name] = $message;
+      // Validate the driver settings and just end here if we have any issues.
+      $connection = NULL;
+      if ($errors = $drivers[$driver]->validateDatabaseSettings($database)) {
+        foreach ($errors as $name => $message) {
+          $this->errors[$name] = $message;
+        }
       }
     }
 
     // Get the Drupal version of the source database so it can be validated.
+    $error_key = $database['driver'] . '][database';
     if (!$this->errors) {
       try {
         $connection = $this->getConnection($database);
@@ -283,6 +343,17 @@ class CredentialForm extends MigrateUpgradeFormBase {
    * Ensures that entered path can be read.
    */
   public function validatePaths($element, FormStateInterface $form_state) {
+    $version = $form_state->getValue('version');
+    // Only validate the paths relevant to the legacy Drupal version.
+    if (($version !== '7')
+      && ($element['#name'] == 'source_base_path' || $element['#name'] == 'source_private_file_path')) {
+      return;
+    }
+
+    if ($version !== '6' && ($element['#name'] == 'd6_source_base_path')) {
+      return;
+    }
+
     if ($source = $element['#value']) {
       $msg = $this->t('Failed to read from @title.', ['@title' => $element['#title']]);
       if (UrlHelper::isExternal($source)) {
diff --git a/core/modules/migrate_drupal_ui/tests/src/FunctionalJavascript/SettingsTest.php b/core/modules/migrate_drupal_ui/tests/src/FunctionalJavascript/SettingsTest.php
new file mode 100644
index 00000000000..776f115f7a6
--- /dev/null
+++ b/core/modules/migrate_drupal_ui/tests/src/FunctionalJavascript/SettingsTest.php
@@ -0,0 +1,274 @@
+<?php
+
+namespace Drupal\Tests\migrate_drupal_ui\FunctionalJavascript;
+
+use Drupal\FunctionalJavascriptTests\WebDriverTestBase;
+
+/**
+ * Tests migrate upgrade credential form with settings in settings.php.
+ *
+ * @group migrate_drupal_ui
+ */
+class SettingsTest extends WebDriverTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = [
+    'migrate',
+    'migrate_drupal',
+    'migrate_drupal_ui',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    // Log in as user 1. Migrations in the UI can only be performed as user 1.
+    $this->drupalLogin($this->rootUser);
+  }
+
+  /**
+   * Test the Credential form with defaults in settings.php.
+   *
+   * @param string|null $source_connection
+   *   The value for the source_connection select field.
+   * @param string $version
+   *   The legacy Drupal version.
+   * @param string[] $manual
+   *   User entered form values.
+   * @param string[] $databases
+   *   Databases data or the settings array.
+   * @param string $expected_source_connection
+   *   The expected source database connection key.
+   *
+   * @throws \Behat\Mink\Exception\ElementNotFoundException
+   * @throws \Behat\Mink\Exception\ExpectationException
+   *
+   * @dataProvider providerTestCredentialForm
+   */
+  public function testCredentialForm($source_connection, $version, array $manual, array $databases, $expected_source_connection) {
+    // Write settings.
+    $migrate_file_public_path = '/var/www/drupal7/sites/default/files';
+    $migrate_file_private_path = '/var/www/drupal7/sites/default/files/private';
+    $settings['settings']['migrate_source_version'] = (object) [
+      'value' => $version,
+      'required' => TRUE,
+    ];
+    $settings['settings']['migrate_source_connection'] = (object) [
+      'value' => $source_connection,
+      'required' => TRUE,
+    ];
+    $settings['settings']['migrate_file_public_path'] = (object) [
+      'value' => $migrate_file_public_path,
+      'required' => TRUE,
+    ];
+    $settings['settings']['migrate_file_private_path'] = (object) [
+      'value' => $migrate_file_private_path,
+      'required' => TRUE,
+    ];
+    foreach ($databases as $key => $value) {
+      $settings['databases'][$key]['default'] = (object) [
+        'value' => $value['default'],
+        'required' => TRUE,
+      ];
+    }
+    $this->writeSettings($settings);
+
+    $edits = [];
+    // Enter the values manually if provided.
+    if (!empty($manual)) {
+      $edit = [];
+      $driver = 'mysql';
+      $edit[$driver]['host'] = $manual['host'];
+      $edit[$driver]['database'] = $manual['database'];
+      $edit[$driver]['username'] = $manual['username'];
+      $edit[$driver]['password'] = $manual['password'];
+      $edits = $this->translatePostValues($edit);
+    }
+
+    // Start the upgrade process.
+    $this->drupalGet('/upgrade');
+    $this->submitForm([], 'Continue');
+    $session = $this->assertSession();
+    // The source connection field is only displayed when there are connections
+    // other than default.
+    if (empty($databases)) {
+      $session->fieldNotExists('source_connection');
+    }
+    else {
+      $session->fieldExists('source_connection');
+    }
+
+    // Submit the Credential form.
+    $this->submitForm($edits, 'Review upgrade');
+
+    // Confirm that the form actually submitted. IF it submitted, we should see
+    // error messages about reading files. If there is no error message, that
+    // indicates that the form did not submit.
+    $session->responseContains('Failed to read from Document root');
+
+    // Assert the form values.
+    $session->fieldValueEquals('version', $version);
+
+    // Check the manually entered credentials or simply the database key.
+    if (empty($manual)) {
+      $session->fieldValueEquals('source_connection', $expected_source_connection);
+    }
+    else {
+      $session->fieldValueEquals('mysql[host]', $manual['host']);
+      $session->fieldValueEquals('mysql[database]', $manual['database']);
+      $session->fieldValueEquals('mysql[username]', $manual['username']);
+    }
+
+    // Confirm the file paths are correct.
+    $session->fieldValueEquals('d6_source_base_path', $migrate_file_public_path);
+    $session->fieldValueEquals('source_base_path', $migrate_file_public_path);
+    $session->fieldValueEquals('source_private_file_path', $migrate_file_private_path);
+  }
+
+  /**
+   * Data provider for testCredentialForm.
+   */
+  public function providerTestCredentialForm() {
+    return [
+      'no values in settings.php' => [
+        'source_connection' => "",
+        'version' => '7',
+        'manual' => [
+          'host' => '172.18.0.2',
+          'database' => 'drupal7',
+          'username' => 'kate',
+          'password' => 'pwd',
+        ],
+        'databases' => [],
+        'expected_source_connection' => '',
+      ],
+      'single database in settings, migrate' => [
+        'source_connection' => 'migrate',
+        'version' => '7',
+        'manual' => [],
+        'databases' => [
+          'migrate' => [
+            'default' => [
+              'database' => 'drupal7',
+              'username' => 'user',
+              'password' => 'pwd',
+              'prefix' => 'test',
+              'host' => '172.18.0.3',
+              'port' => '3307',
+              'namespace' => 'Drupal\\Core\\Database\\Driver\\mysql',
+              'driver' => 'mysql',
+            ],
+          ],
+        ],
+        'expected_source_connection' => 'migrate',
+      ],
+      'migrate_source_connection not set' => [
+        'source_connection' => '',
+        'version' => '7',
+        'manual' => [],
+        'databases' => [
+          'migrate' => [
+            'default' => [
+              'database' => 'drupal7',
+              'username' => 'user',
+              'password' => 'pwd',
+              'prefix' => 'test',
+              'host' => '172.18.0.3',
+              'port' => '3307',
+              'namespace' => 'Drupal\\Core\\Database\\Driver\\mysql',
+              'driver' => 'mysql',
+            ],
+          ],
+        ],
+        'expected_source_connection' => 'migrate',
+      ],
+      'single database in settings, legacy' => [
+        'source_connection' => 'legacy',
+        'version' => '6',
+        'manual' => [],
+        'databases' => [
+          'legacy' => [
+            'default' => [
+              'database' => 'drupal6',
+              'username' => 'user',
+              'password' => 'pwd',
+              'prefix' => 'test',
+              'host' => '172.18.0.6',
+              'port' => '3307',
+              'namespace' => 'Drupal\\Core\\Database\\Driver\\mysql',
+              'driver' => 'mysql',
+            ],
+          ],
+        ],
+        'expected_source_connection' => 'legacy',
+      ],
+      'two databases in settings' => [
+        'source_connection' => 'source2',
+        'version' => '7',
+        'manual' => [],
+        'databases' => [
+          'migrate' => [
+            'default' => [
+              'database' => 'drupal7',
+              'username' => 'user',
+              'password' => 'pwd',
+              'prefix' => 'test',
+              'host' => '172.18.0.3',
+              'port' => '3307',
+              'namespace' => 'Drupal\\Core\\Database\\Driver\\mysql',
+              'driver' => 'mysql',
+            ],
+          ],
+          'legacy' => [
+            'default' => [
+              'database' => 'site',
+              'username' => 'user',
+              'password' => 'pwd',
+              'prefix' => 'test',
+              'host' => '172.18.0.2',
+              'port' => '3307',
+              'namespace' => 'Drupal\\Core\\Database\\Driver\\mysql',
+              'driver' => 'mysql',
+            ],
+          ],
+        ],
+        'expected_source_connection' => 'migrate',
+      ],
+      'database in settings, but use manual' => [
+        'source_connection' => '',
+        'version' => '7',
+        'manual' => [
+          'host' => '172.18.0.2',
+          'database' => 'drupal7',
+          'username' => 'kate',
+          'password' => 'pwd',
+        ],
+        'databases' => [
+          'legacy' => [
+            'default' => [
+              'database' => 'site',
+              'username' => 'user',
+              'password' => 'pwd',
+              'prefix' => 'test',
+              'host' => '172.18.0.2',
+              'port' => '3307',
+              'namespace' => 'Drupal\\Core\\Database\\Driver\\mysql',
+              'driver' => 'mysql',
+            ],
+          ],
+        ],
+        'expected_source_connection' => '',
+      ],
+    ];
+  }
+
+}
diff --git a/sites/default/default.settings.php b/sites/default/default.settings.php
index 5784a9c7523..ee3b49c0a8d 100644
--- a/sites/default/default.settings.php
+++ b/sites/default/default.settings.php
@@ -765,6 +765,49 @@ $settings['entity_update_backup'] = TRUE;
  */
 $settings['migrate_node_migrate_type_classic'] = FALSE;
 
+/**
+ * The default settings for migration sources.
+ *
+ * These settings are used as the default settings on the Credential form at
+ * /upgrade/credentials.
+ *
+ * - migrate_source_version - The version of the source database. This can be
+ *   '6' or '7'. Defaults to '7'.
+ * - migrate_source_connection - The key in the $databases array for the source
+ *   site.
+ * - migrate_file_public_path - The location of the source Drupal 6 or Drupal 7
+ *   public files. This can be a local file directory containing the source
+ *   Drupal 6 or Drupal 7 site (e.g /var/www/docroot), or the site address
+ *   (e.g http://example.com).
+ * - migrate_file_private_path - The location of the source Drupal 7 private
+ *   files. This can be a local file directory containing the source Drupal 7
+ *   site (e.g /var/www/docroot), or empty to use the same value as Public
+ *   files directory.
+ *
+ * Sample configuration for a drupal 6 source site with the source files in a
+ * local directory.
+ *
+ * @code
+ * $settings['migrate_source_version'] = '6';
+ * $settings['migrate_source_connection'] = 'migrate';
+ * $settings['migrate_file_public_path'] = '/var/www/drupal6';
+ * @endcode
+ *
+ * Sample configuration for a drupal 7 source site with public source files on
+ * the source site and the private files in a local directory.
+ *
+ * @code
+ * $settings['migrate_source_version'] = '7';
+ * $settings['migrate_source_connection'] = 'migrate';
+ * $settings['migrate_file_public_path'] = 'https://drupal7.com';
+ * $settings['migrate_file_private_path'] = '/var/www/drupal7';
+ * @endcode
+ */
+# $settings['migrate_source_connection'] = '';
+# $settings['migrate_source_version'] = '';
+# $settings['migrate_file_public_path'] = '';
+# $settings['migrate_file_private_path'] = '';
+
 /**
  * Load local development override configuration, if available.
  *