diff --git a/metatag.module b/metatag.module
index e278685..56ad797 100644
--- a/metatag.module
+++ b/metatag.module
@@ -690,38 +690,7 @@ function metatag_migrate_prepare_row(Row $row, MigrateSourceInterface $source, M
       }
     }
 
-    // Keep a list of the D7 meta tags and how they translate to D8.
-    $tags_map = MigrateHelper::mapForMetatagD7();
-
-    $metatags = [];
-    foreach ($query->execute()->fetchCol() as $data_entry) {
-      // Re-shape D7 entries into for D8 entries.
-      // @todo This could live in a migrate process plugin.
-      foreach (unserialize($data_entry) as $d7_metatag_name => $data) {
-        // If there's no data for this tag, ignore everything.
-        if (empty($data)) {
-          continue;
-        }
-
-        // @todo Skip these values for now, maybe an some version supported
-        // these?
-        if (!is_array($data) || empty($data['value'])) {
-          continue;
-        }
-
-        // Convert the D7 meta tag name to the D8 equivalent. If this meta tag
-        // is not recognized, skip it.
-        if (empty($tags_map[$d7_metatag_name])) {
-          continue;
-        }
-        $d8_metatag_name = $tags_map[$d7_metatag_name];
-
-        // Keep the entire data structure.
-        $metatags[$d8_metatag_name] = $data;
-      }
-    }
-
-    $row->setSourceProperty('pseudo_metatag_d7', serialize($metatags));
+    $row->setSourceProperty('pseudo_metatag_d7', $query->execute()->fetchCol());
   }
 }
 
@@ -741,7 +710,10 @@ function metatag_migration_plugins_alter(array &$migrations) {
       $destination_plugin = DefaultFactory::getPluginClass($migration['destination']['plugin'], $plugin_definition);
 
       if (is_subclass_of($destination_plugin, EntityContentBase::class) || $destination_plugin == EntityContentBase::class) {
-        $migration['process']['field_metatag'] = 'pseudo_metatag_d7';
+        $migration['process']['field_metatag'] = [
+          'process' => 'metatag_d7',
+          'source' => 'pseudo_metatag_d7',
+        ];
       }
     }
   }
diff --git a/src/MigrateHelper.php b/src/MigrateHelper.php
deleted file mode 100644
index 929130b..0000000
--- a/src/MigrateHelper.php
+++ /dev/null
@@ -1,356 +0,0 @@
-<?php
-
-namespace Drupal\metatag;
-
-/**
- * Helpers for migrating data using Migrate API.
- */
-class MigrateHelper {
-
-  /**
-   * A list of D7 meta tags and
-   *
-   * @return array
-   *   An array of D7 tags to their D8 counterparts.
-   */
-  static public function mapForMetatagD7() {
-    $map = [
-      // From the main Metatag module.
-      'abstract' => 'abstract',
-      // @todo 'cache-control' => '',
-      'canonical' => 'canonical_url',
-      'content-language' => 'content_language',
-      'description' => 'description',
-      // @todo 'expires' => '',
-      'generator' => 'generator',
-      'geo.placename' => 'geo_placename',
-      'geo.position' => 'geo_position',
-      'geo.region' => 'geo_region',
-      'icbm' => 'icbm',
-      'image_src' => 'image_src',
-      'keywords' => 'keywords',
-      'news_keywords' => 'news_keywords',
-      // @todo 'next' => '',
-      'original-source' => 'original_source',
-      // @todo 'pragma' => '',
-      // @todo 'prev' => '',
-      'rating' => 'rating',
-      'referrer' => 'referrer',
-      // @todo 'refresh' => '',
-      // @todo 'revisit-after' => '',
-      'rights' => 'rights',
-      'robots' => 'robots',
-      'set_cookie' => 'set_cookie',
-      'shortlink' => 'shortlink',
-      'standout' => 'standout',
-      'title' => 'title',
-      // From metatag_app_links.metatag.inc:
-      'al:android:app_name' => 'al_android_app_name',
-      'al:android:class' => 'al_android_class',
-      'al:android:package' => 'al_android_package',
-      'al:android:url' => 'al_android_url',
-      'al:ios:app_name' => 'al_ios_app_name',
-      'al:ios:app_store_id' => 'al_ios_app_store_id',
-      'al:ios:url' => 'al_ios_url',
-      'al:ipad:app_name' => 'al_ipad_app_name',
-      'al:ipad:app_store_id' => 'al_ipad_app_store_id',
-      'al:ipad:url' => 'al_ipad_url',
-      'al:iphone:app_name' => 'al_iphone_app_name',
-      'al:iphone:app_store_id' => 'al_iphone_app_store_id',
-      'al:iphone:url' => 'al_iphone_url',
-      'al:web:should_fallback' => 'al_web_should_fallback',
-      'al:web:url' => 'al_web_url',
-      'al:windows:app_id' => 'al_windows_app_id',
-      'al:windows:app_name' => 'al_windows_app_name',
-      'al:windows:url' => 'al_windows_url',
-      'al:windows_phone:app_id' => 'al_windows_phone_app_id',
-      'al:windows_phone:app_name' => 'al_windows_phone_app_name',
-      'al:windows_phone:url' => 'al_windows_phone_url',
-      'al:windows_universal:app_id' => 'al_windows_universal_app_id',
-      'al:windows_universal:app_name' => 'al_windows_universal_app_name',
-      'al:windows_universal:url' => 'al_windows_universal_url',
-      // From metatag_dc.metatag.inc:
-      'dcterms.contributor' => 'dcterms_contributor',
-      'dcterms.coverage' => 'dcterms_coverage',
-      'dcterms.creator' => 'dcterms_creator',
-      'dcterms.date' => 'dcterms_date',
-      'dcterms.description' => 'dcterms_description',
-      'dcterms.format' => 'dcterms_format',
-      'dcterms.identifier' => 'dcterms_identifier',
-      'dcterms.language' => 'dcterms_language',
-      'dcterms.publisher' => 'dcterms_publisher',
-      'dcterms.relation' => 'dcterms_relation',
-      'dcterms.rights' => 'dcterms_rights',
-      'dcterms.source' => 'dcterms_source',
-      'dcterms.subject' => 'dcterms_subject',
-      'dcterms.title' => 'dcterms_title',
-      'dcterms.type' => 'dcterms_type',
-      // From metatag_dc_advanced.metatag.inc:
-      'dcterms.abstract' => 'dcterms_abstract',
-      'dcterms.accessRights' => 'dcterms_access_rights',
-      'dcterms.accrualMethod' => 'dcterms_accrual_method',
-      'dcterms.accrualPeriodicity' => 'dcterms_accrual_periodicity',
-      'dcterms.accrualPolicy' => 'dcterms_accrual_policy',
-      'dcterms.alternative' => 'dcterms_alternative',
-      'dcterms.audience' => 'dcterms_audience',
-      'dcterms.available' => 'dcterms_available',
-      'dcterms.bibliographicCitation' => 'dcterms_bibliographic_citation',
-      'dcterms.conformsTo' => 'dcterms_conforms_to',
-      'dcterms.created' => 'dcterms_created',
-      'dcterms.dateAccepted' => 'dcterms_date_accepted',
-      'dcterms.dateCopyrighted' => 'dcterms_date_copyrighted',
-      'dcterms.dateSubmitted' => 'dcterms_date_submitted',
-      'dcterms.educationLevel' => 'dcterms_education_level',
-      'dcterms.extent' => 'dcterms_extent',
-      'dcterms.hasFormat' => 'dcterms_has_format',
-      'dcterms.hasPart' => 'dcterms_has_part',
-      'dcterms.hasVersion' => 'dcterms_has_version',
-      'dcterms.instructionalMethod' => 'dcterms_instructional_method',
-      'dcterms.isFormatOf' => 'dcterms_is_format_of',
-      'dcterms.isPartOf' => 'dcterms_is_part_of',
-      'dcterms.isReferencedBy' => 'dcterms_is_referenced_by',
-      'dcterms.isReplacedBy' => 'dcterms_is_replaced_by',
-      'dcterms.isRequiredBy' => 'dcterms_is_required_by',
-      'dcterms.issued' => 'dcterms_issued',
-      'dcterms.isVersionOf' => 'dcterms_is_version_of',
-      'dcterms.license' => 'dcterms_license',
-      'dcterms.mediator' => 'dcterms_mediator',
-      'dcterms.medium' => 'dcterms_medium',
-      'dcterms.modified' => 'dcterms_modified',
-      'dcterms.provenance' => 'dcterms_provenance',
-      'dcterms.references' => 'dcterms_references',
-      'dcterms.replaces' => 'dcterms_replaces',
-      'dcterms.requires' => 'dcterms_requires',
-      'dcterms.rightsHolder' => 'dcterms_rights_holder',
-      'dcterms.spatial' => 'dcterms_spatial',
-      'dcterms.tableOfContents' => 'dcterms_table_of_contents',
-      'dcterms.temporal' => 'dcterms_temporal',
-      'dcterms.valid' => 'dcterms_valid',
-      // From metatag_facebook.metatag.inc:
-      'fb:admins' => 'fb_admins',
-      'fb:app_id' => 'fb_app_id',
-      'fb:pages' => 'fb_pages',
-      // From metatag_favicons.metatag.inc:
-      'apple-touch-icon' => 'apple_touch_icon',
-      'apple-touch-icon-precomposed' => 'apple_touch_icon_precomposed',
-      'apple-touch-icon-precomposed_114x114' => 'apple_touch_icon_precomposed_114x114',
-      'apple-touch-icon-precomposed_120x120' => 'apple_touch_icon_precomposed_120x120',
-      'apple-touch-icon-precomposed_144x144' => 'apple_touch_icon_precomposed_144x144',
-      'apple-touch-icon-precomposed_152x152' => 'apple_touch_icon_precomposed_152x152',
-      'apple-touch-icon-precomposed_180x180' => 'apple_touch_icon_precomposed_180x180',
-      'apple-touch-icon-precomposed_72x72' => 'apple_touch_icon_precomposed_72x72',
-      'apple-touch-icon-precomposed_76x76' => 'apple_touch_icon_precomposed_76x76',
-      'apple-touch-icon_114x114' => 'apple_touch_icon_114x114',
-      'apple-touch-icon_120x120' => 'apple_touch_icon_120x120',
-      'apple-touch-icon_144x144' => 'apple_touch_icon_144x144',
-      'apple-touch-icon_152x152' => 'apple_touch_icon_152x152',
-      'apple-touch-icon_180x180' => 'apple_touch_icon_180x180',
-      'apple-touch-icon_72x72' => 'apple_touch_icon_72x72',
-      'apple-touch-icon_76x76' => 'apple_touch_icon_76x76',
-      'icon_16x16' => 'icon_16x16',
-      'icon_192x192' => 'icon_192x192',
-      'icon_32x32' => 'icon_32x32',
-      'icon_96x96' => 'icon_96x96',
-      'mask-icon' => 'mask-icon',
-      'shortcut icon' => 'shortcut_icon',
-      // From metatag_google_cse.metatag.inc:
-      'audience' => 'audience',
-      'department' => 'department',
-      'doc_status' => 'doc_status',
-      'google_rating' => 'google_rating',
-      'thumbnail' => 'thumbnail',
-      // From metatag_google_plus.metatag.inc; not doing these, Google+ closed.
-      'itemtype' => '',
-      'itemprop:name' => '',
-      'itemprop:description' => '',
-      'itemprop:image' => '',
-      'author' => '',
-      'publisher' => '',
-      // From metatag_hreflang.metatag.inc:
-      'hreflang_xdefault' => 'hreflang_xdefault',
-      // @todo 'hreflang_' . $langcode => 'hreflang_per_language',
-      // From metatag_mobile.metatag.inc:
-      // @todo 'alternate_handheld' => '',
-      // @todo 'amphtml' => '',
-      'android-app-link-alternative' => 'android_app_link_alternative',
-      'android-manifest' => 'android_manifest',
-      'apple-itunes-app' => 'apple_itunes_app',
-      'apple-mobile-web-app-capable' => 'apple_mobile_web_app_capable',
-      'apple-mobile-web-app-status-bar-style' => 'apple_mobile_web_app_status_bar_style',
-      'apple-mobile-web-app-title' => 'apple_mobile_web_app_title',
-      'application-name' => 'application_name',
-      'cleartype' => 'cleartype',
-      'format-detection' => 'format_detection',
-      'HandheldFriendly' => 'handheldfriendly',
-      'ios-app-link-alternative' => 'ios_app_link_alternative',
-      'MobileOptimized' => 'mobileoptimized',
-      'msapplication-allowDomainApiCalls' => 'msapplication_allowDomainApiCalls',
-      'msapplication-allowDomainMetaTags' => 'msapplication_allowDomainMetaTags',
-      'msapplication-badge' => 'msapplication_badge',
-      'msapplication-config' => 'msapplication_config',
-      'msapplication-navbutton-color' => 'msapplication_navbutton_color',
-      'msapplication-notification' => 'msapplication_notification',
-      'msapplication-square150x150logo' => 'msapplication_square150x150logo',
-      'msapplication-square310x310logo' => 'msapplication_square310x310logo',
-      'msapplication-square70x70logo' => 'msapplication_square70x70logo',
-      'msapplication-starturl' => 'msapplication_starturl',
-      'msapplication-task' => 'msapplication_task',
-      'msapplication-task-separator' => 'msapplication_task_separator',
-      'msapplication-tilecolor' => 'msapplication_tilecolor',
-      'msapplication-tileimage' => 'msapplication_tileimage',
-      'msapplication-tooltip' => 'msapplication_tooltip',
-      'msapplication-wide310x150logo' => 'msapplication_wide310x150logo',
-      'msapplication-window' => 'msapplication_window',
-      'theme-color' => 'theme_color',
-      'viewport' => 'viewport',
-      'x-ua-compatible' => 'x_ua_compatible',
-      // From metatag_opengraph.metatag.inc:
-      'article:author' => 'article_author',
-      'article:expiration_time' => 'article_expiration_time',
-      'article:modified_time' => 'article_modified_time',
-      'article:published_time' => 'article_published_time',
-      'article:publisher' => 'article_publisher',
-      'article:section' => 'article_section',
-      'article:tag' => 'article_tag',
-      'book:author' => 'book_author',
-      'book:isbn' => 'book_isbn',
-      'book:release_date' => 'book_release_date',
-      'book:tag' => 'book_tag',
-      // @todo 'og:audio' => '',
-      // @todo 'og:audio:secure_url' => '',
-      // @todo 'og:audio:type' => '',
-      'og:country_name' => 'og_country_name',
-      'og:description' => 'og_description',
-      'og:determiner' => 'og_determiner',
-      'og:email' => 'og_email',
-      'og:fax_number' => 'og_fax_number',
-      'og:image' => 'og_image',
-      // @todo '' => 'og_image_alt',
-      'og:image:height' => 'og_image_height',
-      'og:image:secure_url' => 'og_image_secure_url',
-      'og:image:type' => 'og_image_type',
-      'og:image:url' => 'og_image_url',
-      'og:image:width' => 'og_image_width',
-      'og:latitude' => 'og_latitude',
-      'og:locale' => 'og_locale',
-      'og:locale:alternate' => 'og_locale_alternative',
-      'og:locality' => 'og_locality',
-      'og:longitude' => 'og_longitude',
-      'og:phone_number' => 'og_phone_number',
-      'og:postal_code' => 'og_postal_code',
-      'og:region' => 'og_region',
-      'og:see_also' => 'og_see_also',
-      'og:site_name' => 'og_site_name',
-      'og:street_address' => 'og_street_address',
-      'og:title' => 'og_title',
-      'og:type' => 'og_type',
-      'og:updated_time' => 'og_updated_time',
-      'og:url' => 'og_url',
-      // @todo '' => 'og_video',
-      'og:video:height' => 'og_video_height',
-      'og:video:secure_url' => 'og_video_secure_url',
-      'og:video:type' => 'og_video_type',
-      'og:video:url' => 'og_video_url',
-      'og:video:width' => 'og_video_width',
-      // @todo 'profile:first_name' => '',
-      // @todo 'profile:gender' => '',
-      // @todo 'profile:last_name' => '',
-      // @todo 'profile:username' => '',
-      // @todo 'video:actor' => '',
-      // @todo 'video:actor:role' => '',
-      // @todo 'video:director' => '',
-      // @todo 'video:duration' => '',
-      // @todo 'video:release_date' => '',
-      // @todo 'video:series' => '',
-      // @todo 'video:tag' => '',
-      // @todo 'video:writer' => '',
-      // From metatag_opengraph_products.metatag.inc:
-      'product:price:amount' => 'product_price_amount',
-      'product:price:currency' => 'product_price_currency',
-      // @todo 'product:availability' => '',
-      // @todo 'product:brand' => '',
-      // @todo 'product:upc' => '',
-      // @todo 'product:ean' => '',
-      // @todo 'product:isbn' => '',
-      // @todo 'product:plural_title' => '',
-      // @todo 'product:retailer' => '',
-      // @todo 'product:retailer_title' => '',
-      // @todo 'product:retailer_part_no' => '',
-      // @todo 'product:mfr_part_no' => '',
-      // @todo 'product:size' => '',
-      // @todo 'product:product_link' => '',
-      // @todo 'product:category' => '',
-      // @todo 'product:color' => '',
-      // @todo 'product:material' => '',
-      // @todo 'product:pattern' => '',
-      // @todo 'product:shipping_cost:amount' => '',
-      // @todo 'product:shipping_cost:currency' => '',
-      // @todo 'product:weight:value' => '',
-      // @todo 'product:weight:units' => '',
-      // @todo 'product:shipping_weight:value' => '',
-      // @todo 'product:shipping_weight:units' => '',
-      // @todo 'product:expiration_time' => '',
-      // @todo 'product:condition' => '',
-      // Pinterest.
-      // @todo '' => 'pinterest_id',
-      // @todo '' => 'pinterest_description',
-      // @todo '' => 'pinterest_nohover',
-      // @todo '' => 'pinterest_url',
-      // @todo '' => 'pinterest_media',
-      // @todo '' => 'pinterest_nopin',
-      // @todo '' => 'pinterest_nosearch',
-      // From metatag_twitter_cards.metatag.inc:
-      'twitter:app:country' => 'twitter_cards_app_store_country',
-      'twitter:app:id:googleplay' => 'twitter_cards_app_id_googleplay',
-      'twitter:app:id:ipad' => 'twitter_cards_app_id_ipad',
-      'twitter:app:id:iphone' => 'twitter_cards_app_id_iphone',
-      'twitter:app:name:googleplay' => 'twitter_cards_app_name_googleplay',
-      'twitter:app:name:ipad' => 'twitter_cards_app_name_ipad',
-      'twitter:app:name:iphone' => 'twitter_cards_app_name_iphone',
-      'twitter:app:url:googleplay' => 'twitter_cards_app_url_googleplay',
-      'twitter:app:url:ipad' => 'twitter_cards_app_url_ipad',
-      'twitter:app:url:iphone' => 'twitter_cards_app_url_iphone',
-      'twitter:card' => 'twitter_cards_type',
-      'twitter:creator' => 'twitter_cards_creator',
-      'twitter:creator:id' => 'twitter_cards_creator_id',
-      'twitter:data1' => 'twitter_cards_data1',
-      'twitter:data2' => 'twitter_cards_data2',
-      'twitter:description' => 'twitter_cards_description',
-      'twitter:dnt' => 'twitter_cards_donottrack',
-      'twitter:image' => 'twitter_cards_image',
-      'twitter:image0' => 'twitter_cards_gallery_image0',
-      'twitter:image1' => 'twitter_cards_gallery_image1',
-      'twitter:image2' => 'twitter_cards_gallery_image2',
-      'twitter:image3' => 'twitter_cards_gallery_image3',
-      'twitter:image:alt' => 'twitter_cards_image_alt',
-      'twitter:image:height' => 'twitter_cards_image_height',
-      'twitter:image:width' => 'twitter_cards_image_width',
-      'twitter:label1' => 'twitter_cards_label1',
-      'twitter:label2' => 'twitter_cards_label2',
-      'twitter:player' => 'twitter_cards_player',
-      'twitter:player:height' => 'twitter_cards_player_height',
-      'twitter:player:stream' => 'twitter_cards_player_stream',
-      'twitter:player:stream:content_type' => 'twitter_cards_player_stream_content_type',
-      'twitter:player:width' => 'twitter_cards_player_width',
-      'twitter:site' => 'twitter_cards_site',
-      'twitter:site:id' => 'twitter_cards_site_id',
-      'twitter:title' => 'twitter_cards_title',
-      'twitter:url' => 'twitter_cards_page_url',
-      // From metatag_verification.metatag.inc:
-      'baidu-site-verification' => 'baidu',
-      'google-site-verification' => 'bing',
-      'msvalidate.01' => 'google',
-      'norton-safeweb-site-verification' => 'norton_safe_web',
-      'p:domain_verify' => 'pinterest',
-      // @todo '' => 'pocket',
-      'yandex-verification' => 'yandex',
-    ];
-
-    // Trigger hook_metatag_migrate_tags_map_alter().
-    // Allow modules to override tags or the entity used for token replacements.
-    \Drupal::service('module_handler')->alter('metatag_migrate_tags_map', $map);
-
-    return $map;
-  }
-
-}
diff --git a/src/Plugin/migrate/process/d7/MetatagD7.php b/src/Plugin/migrate/process/d7/MetatagD7.php
new file mode 100644
index 0000000..3fa897b
--- /dev/null
+++ b/src/Plugin/migrate/process/d7/MetatagD7.php
@@ -0,0 +1,409 @@
+<?php
+
+namespace Drupal\metatag\Plugin\migrate\process;
+
+use Drupal\migrate\MigrateException;
+use Drupal\migrate\MigrateExecutableInterface;
+use Drupal\migrate\ProcessPluginBase;
+use Drupal\migrate\Row;
+
+/**
+ * Migrate data from Metatag-D7.
+ *
+ * @MigrateProcessPlugin(
+ *   id = "metatag_d7",
+ *   handle_multiples = TRUE
+ * )
+ */
+class MetatagD7 {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function transform($value, MigrateExecutableInterface $migrate_executable, Row $row, $destination_property) {
+    $tags_map = $this->tagsMap();
+
+    $metatags = [];
+
+    // Re-shape D7 entries into for D8 entries.
+    try {
+      $old_tags = unserialize($value);
+    }
+    catch (\Exception $e) {
+      throw new MigrateException('Data from Metatag was not a serialized array;' . $e->getMessage());
+    }
+
+    foreach ($old_tags as $d7_metatag_name => $data) {
+      // If there's no data for this tag, ignore everything.
+      if (empty($data)) {
+        continue;
+      }
+
+      // @todo Skip these values for now, maybe some version supported these?
+      if (!is_array($data) || empty($data['value'])) {
+        continue;
+      }
+
+      // Convert the D7 meta tag name to the D8 equivalent. If this meta tag
+      // is not recognized, skip it.
+      if (empty([$d7_metatag_name])) {
+        continue;
+      }
+
+      // There's a D8 equivalent for this meta tag.
+      $d8_metatag_name = $tags_map[$d7_metatag_name];
+
+      // Keep the entire data structure.
+      $metatags[$d8_metatag_name] = $data;
+    }
+
+    return serialize($metatags);
+  }
+
+  /**
+   * Match Metatag-D7 meta tags with their D8 counterparts.
+   *
+   * @return array
+   *   An array of D7 tags to their D8 counterparts.
+   */
+  public function tagsMap() {
+    $map = [
+      // From the main Metatag module.
+      'abstract' => 'abstract',
+      // @todo 'cache-control' => '',
+      'canonical' => 'canonical_url',
+      'content-language' => 'content_language',
+      'description' => 'description',
+      // @todo 'expires' => '',
+      'generator' => 'generator',
+      'geo.placename' => 'geo_placename',
+      'geo.position' => 'geo_position',
+      'geo.region' => 'geo_region',
+      'icbm' => 'icbm',
+      'image_src' => 'image_src',
+      'keywords' => 'keywords',
+      'news_keywords' => 'news_keywords',
+      // @todo 'next' => '',
+      'original-source' => 'original_source',
+      // @todo 'pragma' => '',
+      // @todo 'prev' => '',
+      'rating' => 'rating',
+      'referrer' => 'referrer',
+      // @todo 'refresh' => '',
+      // @todo 'revisit-after' => '',
+      'rights' => 'rights',
+      'robots' => 'robots',
+      'set_cookie' => 'set_cookie',
+      'shortlink' => 'shortlink',
+      'standout' => 'standout',
+      'title' => 'title',
+      // From metatag_app_links.metatag.inc:
+      'al:android:app_name' => 'al_android_app_name',
+      'al:android:class' => 'al_android_class',
+      'al:android:package' => 'al_android_package',
+      'al:android:url' => 'al_android_url',
+      'al:ios:app_name' => 'al_ios_app_name',
+      'al:ios:app_store_id' => 'al_ios_app_store_id',
+      'al:ios:url' => 'al_ios_url',
+      'al:ipad:app_name' => 'al_ipad_app_name',
+      'al:ipad:app_store_id' => 'al_ipad_app_store_id',
+      'al:ipad:url' => 'al_ipad_url',
+      'al:iphone:app_name' => 'al_iphone_app_name',
+      'al:iphone:app_store_id' => 'al_iphone_app_store_id',
+      'al:iphone:url' => 'al_iphone_url',
+      'al:web:should_fallback' => 'al_web_should_fallback',
+      'al:web:url' => 'al_web_url',
+      'al:windows:app_id' => 'al_windows_app_id',
+      'al:windows:app_name' => 'al_windows_app_name',
+      'al:windows:url' => 'al_windows_url',
+      'al:windows_phone:app_id' => 'al_windows_phone_app_id',
+      'al:windows_phone:app_name' => 'al_windows_phone_app_name',
+      'al:windows_phone:url' => 'al_windows_phone_url',
+      'al:windows_universal:app_id' => 'al_windows_universal_app_id',
+      'al:windows_universal:app_name' => 'al_windows_universal_app_name',
+      'al:windows_universal:url' => 'al_windows_universal_url',
+      // From metatag_dc.metatag.inc:
+      'dcterms.contributor' => 'dcterms_contributor',
+      'dcterms.coverage' => 'dcterms_coverage',
+      'dcterms.creator' => 'dcterms_creator',
+      'dcterms.date' => 'dcterms_date',
+      'dcterms.description' => 'dcterms_description',
+      'dcterms.format' => 'dcterms_format',
+      'dcterms.identifier' => 'dcterms_identifier',
+      'dcterms.language' => 'dcterms_language',
+      'dcterms.publisher' => 'dcterms_publisher',
+      'dcterms.relation' => 'dcterms_relation',
+      'dcterms.rights' => 'dcterms_rights',
+      'dcterms.source' => 'dcterms_source',
+      'dcterms.subject' => 'dcterms_subject',
+      'dcterms.title' => 'dcterms_title',
+      'dcterms.type' => 'dcterms_type',
+      // From metatag_dc_advanced.metatag.inc:
+      'dcterms.abstract' => 'dcterms_abstract',
+      'dcterms.accessRights' => 'dcterms_access_rights',
+      'dcterms.accrualMethod' => 'dcterms_accrual_method',
+      'dcterms.accrualPeriodicity' => 'dcterms_accrual_periodicity',
+      'dcterms.accrualPolicy' => 'dcterms_accrual_policy',
+      'dcterms.alternative' => 'dcterms_alternative',
+      'dcterms.audience' => 'dcterms_audience',
+      'dcterms.available' => 'dcterms_available',
+      'dcterms.bibliographicCitation' => 'dcterms_bibliographic_citation',
+      'dcterms.conformsTo' => 'dcterms_conforms_to',
+      'dcterms.created' => 'dcterms_created',
+      'dcterms.dateAccepted' => 'dcterms_date_accepted',
+      'dcterms.dateCopyrighted' => 'dcterms_date_copyrighted',
+      'dcterms.dateSubmitted' => 'dcterms_date_submitted',
+      'dcterms.educationLevel' => 'dcterms_education_level',
+      'dcterms.extent' => 'dcterms_extent',
+      'dcterms.hasFormat' => 'dcterms_has_format',
+      'dcterms.hasPart' => 'dcterms_has_part',
+      'dcterms.hasVersion' => 'dcterms_has_version',
+      'dcterms.instructionalMethod' => 'dcterms_instructional_method',
+      'dcterms.isFormatOf' => 'dcterms_is_format_of',
+      'dcterms.isPartOf' => 'dcterms_is_part_of',
+      'dcterms.isReferencedBy' => 'dcterms_is_referenced_by',
+      'dcterms.isReplacedBy' => 'dcterms_is_replaced_by',
+      'dcterms.isRequiredBy' => 'dcterms_is_required_by',
+      'dcterms.issued' => 'dcterms_issued',
+      'dcterms.isVersionOf' => 'dcterms_is_version_of',
+      'dcterms.license' => 'dcterms_license',
+      'dcterms.mediator' => 'dcterms_mediator',
+      'dcterms.medium' => 'dcterms_medium',
+      'dcterms.modified' => 'dcterms_modified',
+      'dcterms.provenance' => 'dcterms_provenance',
+      'dcterms.references' => 'dcterms_references',
+      'dcterms.replaces' => 'dcterms_replaces',
+      'dcterms.requires' => 'dcterms_requires',
+      'dcterms.rightsHolder' => 'dcterms_rights_holder',
+      'dcterms.spatial' => 'dcterms_spatial',
+      'dcterms.tableOfContents' => 'dcterms_table_of_contents',
+      'dcterms.temporal' => 'dcterms_temporal',
+      'dcterms.valid' => 'dcterms_valid',
+      // From metatag_facebook.metatag.inc:
+      'fb:admins' => 'fb_admins',
+      'fb:app_id' => 'fb_app_id',
+      'fb:pages' => 'fb_pages',
+      // From metatag_favicons.metatag.inc:
+      'apple-touch-icon' => 'apple_touch_icon',
+      'apple-touch-icon-precomposed' => 'apple_touch_icon_precomposed',
+      'apple-touch-icon-precomposed_114x114' => 'apple_touch_icon_precomposed_114x114',
+      'apple-touch-icon-precomposed_120x120' => 'apple_touch_icon_precomposed_120x120',
+      'apple-touch-icon-precomposed_144x144' => 'apple_touch_icon_precomposed_144x144',
+      'apple-touch-icon-precomposed_152x152' => 'apple_touch_icon_precomposed_152x152',
+      'apple-touch-icon-precomposed_180x180' => 'apple_touch_icon_precomposed_180x180',
+      'apple-touch-icon-precomposed_72x72' => 'apple_touch_icon_precomposed_72x72',
+      'apple-touch-icon-precomposed_76x76' => 'apple_touch_icon_precomposed_76x76',
+      'apple-touch-icon_114x114' => 'apple_touch_icon_114x114',
+      'apple-touch-icon_120x120' => 'apple_touch_icon_120x120',
+      'apple-touch-icon_144x144' => 'apple_touch_icon_144x144',
+      'apple-touch-icon_152x152' => 'apple_touch_icon_152x152',
+      'apple-touch-icon_180x180' => 'apple_touch_icon_180x180',
+      'apple-touch-icon_72x72' => 'apple_touch_icon_72x72',
+      'apple-touch-icon_76x76' => 'apple_touch_icon_76x76',
+      'icon_16x16' => 'icon_16x16',
+      'icon_192x192' => 'icon_192x192',
+      'icon_32x32' => 'icon_32x32',
+      'icon_96x96' => 'icon_96x96',
+      'mask-icon' => 'mask-icon',
+      'shortcut icon' => 'shortcut_icon',
+      // From metatag_google_cse.metatag.inc:
+      'audience' => 'audience',
+      'department' => 'department',
+      'doc_status' => 'doc_status',
+      'google_rating' => 'google_rating',
+      'thumbnail' => 'thumbnail',
+      // From metatag_google_plus.metatag.inc; not doing these, Google+ closed.
+      'itemtype' => '',
+      'itemprop:name' => '',
+      'itemprop:description' => '',
+      'itemprop:image' => '',
+      'author' => '',
+      'publisher' => '',
+      // From metatag_hreflang.metatag.inc:
+      'hreflang_xdefault' => 'hreflang_xdefault',
+      // @todo 'hreflang_' . $langcode => 'hreflang_per_language',
+      // From metatag_mobile.metatag.inc:
+      // @todo 'alternate_handheld' => '',
+      // @todo 'amphtml' => '',
+      'android-app-link-alternative' => 'android_app_link_alternative',
+      'android-manifest' => 'android_manifest',
+      'apple-itunes-app' => 'apple_itunes_app',
+      'apple-mobile-web-app-capable' => 'apple_mobile_web_app_capable',
+      'apple-mobile-web-app-status-bar-style' => 'apple_mobile_web_app_status_bar_style',
+      'apple-mobile-web-app-title' => 'apple_mobile_web_app_title',
+      'application-name' => 'application_name',
+      'cleartype' => 'cleartype',
+      'format-detection' => 'format_detection',
+      'HandheldFriendly' => 'handheldfriendly',
+      'ios-app-link-alternative' => 'ios_app_link_alternative',
+      'MobileOptimized' => 'mobileoptimized',
+      'msapplication-allowDomainApiCalls' => 'msapplication_allowDomainApiCalls',
+      'msapplication-allowDomainMetaTags' => 'msapplication_allowDomainMetaTags',
+      'msapplication-badge' => 'msapplication_badge',
+      'msapplication-config' => 'msapplication_config',
+      'msapplication-navbutton-color' => 'msapplication_navbutton_color',
+      'msapplication-notification' => 'msapplication_notification',
+      'msapplication-square150x150logo' => 'msapplication_square150x150logo',
+      'msapplication-square310x310logo' => 'msapplication_square310x310logo',
+      'msapplication-square70x70logo' => 'msapplication_square70x70logo',
+      'msapplication-starturl' => 'msapplication_starturl',
+      'msapplication-task' => 'msapplication_task',
+      'msapplication-task-separator' => 'msapplication_task_separator',
+      'msapplication-tilecolor' => 'msapplication_tilecolor',
+      'msapplication-tileimage' => 'msapplication_tileimage',
+      'msapplication-tooltip' => 'msapplication_tooltip',
+      'msapplication-wide310x150logo' => 'msapplication_wide310x150logo',
+      'msapplication-window' => 'msapplication_window',
+      'theme-color' => 'theme_color',
+      'viewport' => 'viewport',
+      'x-ua-compatible' => 'x_ua_compatible',
+      // From metatag_opengraph.metatag.inc:
+      'article:author' => 'article_author',
+      'article:expiration_time' => 'article_expiration_time',
+      'article:modified_time' => 'article_modified_time',
+      'article:published_time' => 'article_published_time',
+      'article:publisher' => 'article_publisher',
+      'article:section' => 'article_section',
+      'article:tag' => 'article_tag',
+      'book:author' => 'book_author',
+      'book:isbn' => 'book_isbn',
+      'book:release_date' => 'book_release_date',
+      'book:tag' => 'book_tag',
+      // @todo 'og:audio' => '',
+      // @todo 'og:audio:secure_url' => '',
+      // @todo 'og:audio:type' => '',
+      'og:country_name' => 'og_country_name',
+      'og:description' => 'og_description',
+      'og:determiner' => 'og_determiner',
+      'og:email' => 'og_email',
+      'og:fax_number' => 'og_fax_number',
+      'og:image' => 'og_image',
+      // @todo '' => 'og_image_alt',
+      'og:image:height' => 'og_image_height',
+      'og:image:secure_url' => 'og_image_secure_url',
+      'og:image:type' => 'og_image_type',
+      'og:image:url' => 'og_image_url',
+      'og:image:width' => 'og_image_width',
+      'og:latitude' => 'og_latitude',
+      'og:locale' => 'og_locale',
+      'og:locale:alternate' => 'og_locale_alternative',
+      'og:locality' => 'og_locality',
+      'og:longitude' => 'og_longitude',
+      'og:phone_number' => 'og_phone_number',
+      'og:postal_code' => 'og_postal_code',
+      'og:region' => 'og_region',
+      'og:see_also' => 'og_see_also',
+      'og:site_name' => 'og_site_name',
+      'og:street_address' => 'og_street_address',
+      'og:title' => 'og_title',
+      'og:type' => 'og_type',
+      'og:updated_time' => 'og_updated_time',
+      'og:url' => 'og_url',
+      // @todo '' => 'og_video',
+      'og:video:height' => 'og_video_height',
+      'og:video:secure_url' => 'og_video_secure_url',
+      'og:video:type' => 'og_video_type',
+      'og:video:url' => 'og_video_url',
+      'og:video:width' => 'og_video_width',
+      // @todo 'profile:first_name' => '',
+      // @todo 'profile:gender' => '',
+      // @todo 'profile:last_name' => '',
+      // @todo 'profile:username' => '',
+      // @todo 'video:actor' => '',
+      // @todo 'video:actor:role' => '',
+      // @todo 'video:director' => '',
+      // @todo 'video:duration' => '',
+      // @todo 'video:release_date' => '',
+      // @todo 'video:series' => '',
+      // @todo 'video:tag' => '',
+      // @todo 'video:writer' => '',
+      // From metatag_opengraph_products.metatag.inc:
+      'product:price:amount' => 'product_price_amount',
+      'product:price:currency' => 'product_price_currency',
+      // @todo 'product:availability' => '',
+      // @todo 'product:brand' => '',
+      // @todo 'product:upc' => '',
+      // @todo 'product:ean' => '',
+      // @todo 'product:isbn' => '',
+      // @todo 'product:plural_title' => '',
+      // @todo 'product:retailer' => '',
+      // @todo 'product:retailer_title' => '',
+      // @todo 'product:retailer_part_no' => '',
+      // @todo 'product:mfr_part_no' => '',
+      // @todo 'product:size' => '',
+      // @todo 'product:product_link' => '',
+      // @todo 'product:category' => '',
+      // @todo 'product:color' => '',
+      // @todo 'product:material' => '',
+      // @todo 'product:pattern' => '',
+      // @todo 'product:shipping_cost:amount' => '',
+      // @todo 'product:shipping_cost:currency' => '',
+      // @todo 'product:weight:value' => '',
+      // @todo 'product:weight:units' => '',
+      // @todo 'product:shipping_weight:value' => '',
+      // @todo 'product:shipping_weight:units' => '',
+      // @todo 'product:expiration_time' => '',
+      // @todo 'product:condition' => '',
+      // Pinterest.
+      // @todo '' => 'pinterest_id',
+      // @todo '' => 'pinterest_description',
+      // @todo '' => 'pinterest_nohover',
+      // @todo '' => 'pinterest_url',
+      // @todo '' => 'pinterest_media',
+      // @todo '' => 'pinterest_nopin',
+      // @todo '' => 'pinterest_nosearch',
+      // From metatag_twitter_cards.metatag.inc:
+      'twitter:app:country' => 'twitter_cards_app_store_country',
+      'twitter:app:id:googleplay' => 'twitter_cards_app_id_googleplay',
+      'twitter:app:id:ipad' => 'twitter_cards_app_id_ipad',
+      'twitter:app:id:iphone' => 'twitter_cards_app_id_iphone',
+      'twitter:app:name:googleplay' => 'twitter_cards_app_name_googleplay',
+      'twitter:app:name:ipad' => 'twitter_cards_app_name_ipad',
+      'twitter:app:name:iphone' => 'twitter_cards_app_name_iphone',
+      'twitter:app:url:googleplay' => 'twitter_cards_app_url_googleplay',
+      'twitter:app:url:ipad' => 'twitter_cards_app_url_ipad',
+      'twitter:app:url:iphone' => 'twitter_cards_app_url_iphone',
+      'twitter:card' => 'twitter_cards_type',
+      'twitter:creator' => 'twitter_cards_creator',
+      'twitter:creator:id' => 'twitter_cards_creator_id',
+      'twitter:data1' => 'twitter_cards_data1',
+      'twitter:data2' => 'twitter_cards_data2',
+      'twitter:description' => 'twitter_cards_description',
+      'twitter:dnt' => 'twitter_cards_donottrack',
+      'twitter:image' => 'twitter_cards_image',
+      'twitter:image0' => 'twitter_cards_gallery_image0',
+      'twitter:image1' => 'twitter_cards_gallery_image1',
+      'twitter:image2' => 'twitter_cards_gallery_image2',
+      'twitter:image3' => 'twitter_cards_gallery_image3',
+      'twitter:image:alt' => 'twitter_cards_image_alt',
+      'twitter:image:height' => 'twitter_cards_image_height',
+      'twitter:image:width' => 'twitter_cards_image_width',
+      'twitter:label1' => 'twitter_cards_label1',
+      'twitter:label2' => 'twitter_cards_label2',
+      'twitter:player' => 'twitter_cards_player',
+      'twitter:player:height' => 'twitter_cards_player_height',
+      'twitter:player:stream' => 'twitter_cards_player_stream',
+      'twitter:player:stream:content_type' => 'twitter_cards_player_stream_content_type',
+      'twitter:player:width' => 'twitter_cards_player_width',
+      'twitter:site' => 'twitter_cards_site',
+      'twitter:site:id' => 'twitter_cards_site_id',
+      'twitter:title' => 'twitter_cards_title',
+      'twitter:url' => 'twitter_cards_page_url',
+      // From metatag_verification.metatag.inc:
+      'baidu-site-verification' => 'baidu',
+      'google-site-verification' => 'bing',
+      'msvalidate.01' => 'google',
+      'norton-safeweb-site-verification' => 'norton_safe_web',
+      'p:domain_verify' => 'pinterest',
+      // @todo '' => 'pocket',
+      'yandex-verification' => 'yandex',
+    ];
+
+    // Trigger hook_metatag_migrate_tags_map_alter().
+    // Allow modules to override tags or the entity used for token replacements.
+    \Drupal::service('module_handler')->alter('metatag_migrate_tags_map', $map);
+
+    return $map;
+  }
+
+}