diff --git a/admin/qtx_activation_hook.php b/admin/qtx_activation_hook.php
index b410d4b8..2a228791 100644
--- a/admin/qtx_activation_hook.php
+++ b/admin/qtx_activation_hook.php
@@ -787,7 +787,6 @@ function qtranxf_activation_hook() {
     // Migrate (rename/import) legacy options, temporary transitions during evolutions.
     qtranxf_rename_legacy_option( 'qtranslate_modules', QTX_OPTIONS_MODULES_STATE );
     qtranxf_import_legacy_option( 'acf_qtranslate', QTX_OPTIONS_MODULE_ACF, false );
-    qtranxf_import_legacy_option( 'qts_options', QTX_OPTIONS_MODULE_SLUGS, false );
 
     $ts                     = time();
     $next_thanks            = get_option( 'qtranslate_next_thanks' );
@@ -932,6 +931,30 @@ function qtranxf_admin_notices_gutenberg() {
 
 add_action( 'admin_notices', 'qtranxf_admin_notices_gutenberg' );
 
+function qtranxf_admin_notices_slugs_migrate() {
+    if ( qtranxf_check_admin_notice( 'slugs-migrate' ) || ! QTX_Module_Loader::is_module_active( 'slugs' ) ) {
+        return;
+    }
+    $old_value = get_option( 'qts_options' );  // Very quick check to avoid loading more code.
+    if ( ! $old_value ) {
+        return;
+    }
+    require_once( QTRANSLATE_DIR . '/modules/slugs/admin/slugs-migrate-qts.php' );
+    $msg = qtranxf_slugs_check_migrate_qts();  // More advanced checks with QTS meta.
+    if ( empty( $msg ) ) {
+        return;
+    }
+    qtranxf_admin_notice_dismiss_script();
+    echo '<div class="notice notice-warning qtranxs-notice-ajax is-dismissible" id="qtranxs-slugs-migrate"><p>';
+    $options_link = admin_url( 'options-general.php?page=qtranslate-xt#import' );
+    echo '<p>' . sprintf( __( '%s : found slugs meta that can be migrated. Go to the <a href="%s">import settings</a> to migrate.', 'qtranslate' ), qtranxf_get_plugin_link(), $options_link ) . '</p>';
+    echo '<p>' . $msg . '</p>';
+    echo '</p><p><a class="button qtranxs-notice-dismiss" href="javascript:void(0);">' . __( 'I have already done it, dismiss this message.', 'qtranslate' );
+    echo '</a></p></div>';
+}
+
+add_action( 'admin_notices', 'qtranxf_admin_notices_slugs_migrate' );
+
 function qtranxf_admin_notice_deactivate_plugin( $name, $plugin ) {
     deactivate_plugins( $plugin, true );
     $d        = dirname( $plugin );
@@ -1028,6 +1051,14 @@ function qtranxf_update_option_admin_notices( $messages, $id, $set = true ) {
     return $messages;
 }
 
+/**
+ * Update an admin notice to be set (hidden) / unset (shown).
+ *
+ * @param string $id
+ * @param bool $set true to set the message as seen (hide), false to unset (show)
+ *
+ * @return array|mixed
+ */
 function qtranxf_update_admin_notice( $id, $set ) {
     $messages = get_option( 'qtranslate_admin_notices', array() );
 
diff --git a/admin/qtx_admin_options_update.php b/admin/qtx_admin_options_update.php
index 913e6843..ceb1024a 100644
--- a/admin/qtx_admin_options_update.php
+++ b/admin/qtx_admin_options_update.php
@@ -45,6 +45,14 @@ function qtranxf_edit_config() {
     if ( isset( $_POST['qtranslate_reset'] ) && isset( $_POST['qtranslate_reset2'] ) ) {
         $messages[] = __( 'qTranslate has been reset.', 'qtranslate' );
     } elseif ( isset( $_POST['default_language'] ) ) {
+        // TODO: remove temporary hack - restore QTS options for master dev before migration.
+        // Undo import legacy options in master before new options are saved with new keys...
+        $qts_options = get_option( 'qts_options' );
+        $new_options = get_option( QTX_OPTIONS_MODULE_SLUGS );
+        // Re-create original QTS options that can be properly imported again.
+        if ( ! $qts_options && $new_options && count( $new_options ) > 0 && strpos( array_keys( $new_options )[0], '_qts_' ) === 0 ) {
+            update_option( 'qts_options', $new_options, false );
+        }
 
         qtranxf_update_settings();
 
@@ -971,6 +979,12 @@ function qtranxf_executeOnUpdate() {
             $messages[] = $msg;
         }
     }
+
+    if ( isset( $_POST['qtranslate_import_slugs_migrate'] ) && $_POST['qtranslate_import_slugs_migrate'] ) {
+        require_once( QTRANSLATE_DIR . '/modules/slugs/admin/slugs-migrate-qts.php' );
+        $db_commit  = isset( $_POST['qtranslate_import_slugs_confirm'] ) && $_POST['qtranslate_import_slugs_confirm'];
+        $messages[] = qtranxf_slugs_migrate_qts_data( $db_commit );
+    }
 }
 
 function qtranxf_mark_default( $text ) {
diff --git a/admin/qtx_import_export.php b/admin/qtx_import_export.php
index ce816871..138fb9d9 100644
--- a/admin/qtx_import_export.php
+++ b/admin/qtx_import_export.php
@@ -229,6 +229,27 @@ function qtranxf_admin_section_import_export( $request_uri ) {
             'text' => sprintf( __( 'Use plugin %s to import data.', 'qtranslate' ), '<a href="https://wordpress.org/plugins/w2q-wpml-to-qtranslate/" target="_blank">W2Q: WPML to qTranslate</a>' )
         ) ) ?>
         <?php do_action( 'qtranslate_add_row_migrate' ) ?>
+        <?php if ( QTX_Module_Loader::is_module_active( 'slugs' ) ): ?>
+            <tr id="qtranslate-import-slugs">
+                <th scope="row"><?php _e( 'Migrate QTS slugs', 'qtranslate' ) ?></th>
+                <td>
+                    <label for="qtranslate_import_slugs_migrate">
+                        <input type="checkbox" name="qtranslate_import_slugs_migrate"
+                               id="qtranslate_import_slugs_migrate"
+                               value="1"
+                               onclick="let c=jQuery('#qtranslate_import_slugs_confirm'); c.prop('disabled', !jQuery(this).prop('checked')); c.prop('checked', false);"/>
+                        <?php _e( 'Migrate slugs options, post and term meta from legacy QTS plugin to qTranslate.', 'qtranslate' ); ?>
+                    </label>
+                    <br/>
+                    <label for="qtranslate_import_slugs_confirm">
+                        <input type="checkbox"
+                               name="qtranslate_import_slugs_confirm"
+                               id="qtranslate_import_slugs_confirm"
+                               value="1" <?php disabled( true ) ?> /> <?php _e( "Confirm migration of QTS slugs in database. Attention! Existing slugs are replaced. Leave unchecked for a dry-run.", 'qtranslate' ) ?>
+                    </label>
+                </td>
+            </tr>
+        <?php endif ?>
         <tr>
             <th scope="row"><?php _e( 'Reset qTranslate', 'qtranslate' ) ?></th>
             <td>
diff --git a/modules/slugs/admin/slugs-admin.php b/modules/slugs/admin/slugs-admin.php
index 2a91f869..75b0f27c 100644
--- a/modules/slugs/admin/slugs-admin.php
+++ b/modules/slugs/admin/slugs-admin.php
@@ -73,10 +73,11 @@ function qts_uninstall() {
 
     $meta_keys = array();
     foreach ( $q_config['enabled_languages'] as $lang ) {
-        $meta_keys[] = QTS_META_PREFIX . $lang;
+        $meta_keys[] = QTX_SLUGS_META_PREFIX . $lang;
     }
     $meta_keys = "'" . implode( "','", $meta_keys ) . "'";
     $wpdb->query( "DELETE from $wpdb->postmeta WHERE meta_key IN ($meta_keys)" );
+    $wpdb->query( "DELETE from $wpdb->termmeta WHERE meta_key IN ($meta_keys)" );
 
     qts_deactivate();
 
@@ -126,7 +127,7 @@ function qts_draw_meta_box( $post ) {
     echo '<input type="hidden" name="qts_nonce" id="qts_nonce" value="' . wp_create_nonce( 'qts_nonce' ) . '" />' . PHP_EOL;
     $flag_location = qtranxf_flag_location();
     foreach ( $q_config['enabled_languages'] as $lang ):
-        $slug  = get_post_meta( $post->ID, QTS_META_PREFIX . $lang, true );
+        $slug  = get_post_meta( $post->ID, QTX_SLUGS_META_PREFIX . $lang, true );
         $value = ( $slug ) ? htmlspecialchars( $slug, ENT_QUOTES ) : '';
         $name  = $q_config['language_name'][ $lang ];
         $title = sprintf( __( 'Slug' ) . ' (%s)', $name );
@@ -149,7 +150,7 @@ function qts_draw_meta_box( $post ) {
  */
 function qts_sanitize_post_slug( $slug, $post, $lang ) {
     $post_title = trim( qtranxf_use( $lang, $post->post_title ) );
-    $post_name  = get_post_meta( $post->ID, QTS_META_PREFIX . $lang, true );
+    $post_name  = get_post_meta( $post->ID, QTX_SLUGS_META_PREFIX . $lang, true );
     if ( ! $post_name ) {
         $post_name = $post->post_name;
     }
@@ -229,7 +230,7 @@ function qts_wp_unique_post_slug( $slug, $post_ID, $post_status, $post_type, $po
         // TODO: update unique_slug :: missing hieararchical from current wp func ( 4.3.1 )
         // Post slugs must be unique across all posts.
         $check_sql       = "SELECT $wpdb->postmeta.meta_value FROM $wpdb->posts,$wpdb->postmeta WHERE $wpdb->posts.ID = $wpdb->postmeta.post_id AND $wpdb->postmeta.meta_key = '%s' AND $wpdb->postmeta.meta_value = '%s' AND $wpdb->posts.post_type = %s AND $wpdb->posts.ID != %d LIMIT 1";
-        $post_name_check = $wpdb->get_var( $wpdb->prepare( $check_sql, QTS_META_PREFIX . $lang, $slug, $post_type, $post_ID ) );
+        $post_name_check = $wpdb->get_var( $wpdb->prepare( $check_sql, QTX_SLUGS_META_PREFIX . $lang, $slug, $post_type, $post_ID ) );
 
         // TODO: update unique_slug :: missing check for conflict with dates archive from current wp func ( 4.3.1 )
         if ( $post_name_check || in_array( $slug, $feeds ) || apply_filters( 'wp_unique_post_slug_is_bad_flat_slug', false, $slug, $post_type ) ) {
@@ -237,7 +238,7 @@ function qts_wp_unique_post_slug( $slug, $post_ID, $post_status, $post_type, $po
             do {
                 // TODO: update unique_slug :: same as above: differs from current wp func ( 4.3.1 )
                 $alt_post_name   = substr( $slug, 0, 200 - ( strlen( $suffix ) + 1 ) ) . "-$suffix";
-                $post_name_check = $wpdb->get_var( $wpdb->prepare( $check_sql, QTS_META_PREFIX . $lang, $alt_post_name, $post_type, $post_ID ) );
+                $post_name_check = $wpdb->get_var( $wpdb->prepare( $check_sql, QTX_SLUGS_META_PREFIX . $lang, $alt_post_name, $post_type, $post_ID ) );
                 $suffix++;
             } while ( $post_name_check );
             $slug = $alt_post_name;
@@ -276,8 +277,8 @@ function qts_save_postdata( $post_id, $post = null ) {
             $slug = qts_sanitize_post_slug( $slug, $post, $lang );
             $slug = qts_unique_post_slug( $slug, $post, $lang );
 
-            delete_post_meta( $post_id, QTS_META_PREFIX . $lang );
-            update_post_meta( $post_id, QTS_META_PREFIX . $lang, $slug );
+            delete_post_meta( $post_id, QTX_SLUGS_META_PREFIX . $lang );
+            update_post_meta( $post_id, QTX_SLUGS_META_PREFIX . $lang, $slug );
         }
     }
 }
@@ -318,7 +319,7 @@ function qts_sanitize_term_slug( $slug, $term, $lang ) {
 function qts_unique_term_slug( $slug, $term, $lang ) {
     global $wpdb;
 
-    $query       = $wpdb->prepare( "SELECT term_id FROM $wpdb->termmeta WHERE meta_key = '%s' AND meta_value = '%s' AND term_id != %d ", QTS_META_PREFIX . $lang, $slug, $term->term_id );
+    $query       = $wpdb->prepare( "SELECT term_id FROM $wpdb->termmeta WHERE meta_key = '%s' AND meta_value = '%s' AND term_id != %d ", QTX_SLUGS_META_PREFIX . $lang, $slug, $term->term_id );
     $exists_slug = $wpdb->get_results( $query );
 
     if ( empty( $exists_slug ) ) {
@@ -326,7 +327,7 @@ function qts_unique_term_slug( $slug, $term, $lang ) {
     }
 
     // If we didn't get a unique slug, try appending a number to make it unique.
-    $query = $wpdb->prepare( "SELECT meta_value FROM $wpdb->termmeta WHERE meta_key = '%s' AND meta_value = '%s' AND term_id != %d", QTS_META_PREFIX . $lang, $slug, $term->term_id );
+    $query = $wpdb->prepare( "SELECT meta_value FROM $wpdb->termmeta WHERE meta_key = '%s' AND meta_value = '%s' AND term_id != %d", QTX_SLUGS_META_PREFIX . $lang, $slug, $term->term_id );
 
     if ( $wpdb->get_var( $query ) ) {
         $num = 2;
@@ -336,7 +337,7 @@ function qts_unique_term_slug( $slug, $term, $lang ) {
             $slug_check = $wpdb->get_var(
                 $wpdb->prepare(
                     "SELECT meta_value FROM $wpdb->termmeta WHERE meta_key = '%s' AND meta_value = '%s'",
-                    QTS_META_PREFIX . $lang,
+                    QTX_SLUGS_META_PREFIX . $lang,
                     $alt_slug ) );
         } while ( $slug_check );
         $slug = $alt_slug;
@@ -371,8 +372,8 @@ function qts_save_term( $term_id, $tt_id, $taxonomy ) {
         $slug = qts_sanitize_term_slug( $slug, $term, $lang );
         $slug = qts_unique_term_slug( $slug, $term, $lang );
 
-        delete_metadata( 'term', $term_id, QTS_META_PREFIX . $lang );
-        update_metadata( 'term', $term_id, QTS_META_PREFIX . $lang, $slug );
+        delete_metadata( 'term', $term_id, QTX_SLUGS_META_PREFIX . $lang );
+        update_metadata( 'term', $term_id, QTX_SLUGS_META_PREFIX . $lang, $slug );
     }
 }
 
@@ -389,7 +390,7 @@ function qts_show_list_term_fields( $term ) {
     $flag_location = qtranxf_flag_location(); ?>
     <ul class="qtranxs-slugs-list qtranxs-slugs-terms"><?php
         foreach ( $q_config['enabled_languages'] as $lang ) {
-            $slug  = is_object( $term ) ? get_metadata( 'term', $term->term_id, QTS_META_PREFIX . $lang, true ) : '';
+            $slug  = is_object( $term ) ? get_metadata( 'term', $term->term_id, QTX_SLUGS_META_PREFIX . $lang, true ) : '';
             $value = $slug ? htmlspecialchars( $slug, ENT_QUOTES ) : '';
             $flag  = $q_config['flag'][ $lang ];
             $name  = $q_config['language_name'][ $lang ];
@@ -532,7 +533,7 @@ function qts_taxonomy_custom_column( $str, $column_name, $term_id ) {
     global $q_config;
 
     if ( $column_name === 'qts-slug' ) {
-        echo get_metadata( 'term', $term_id, QTS_META_PREFIX . $q_config['language'], true );
+        echo get_metadata( 'term', $term_id, QTX_SLUGS_META_PREFIX . $q_config['language'], true );
     }
 
     return false;
diff --git a/modules/slugs/admin/slugs-migrate-qts.php b/modules/slugs/admin/slugs-migrate-qts.php
new file mode 100644
index 00000000..ae814c7e
--- /dev/null
+++ b/modules/slugs/admin/slugs-migrate-qts.php
@@ -0,0 +1,165 @@
+<?php
+/**
+ * Legacy meta and options from QTS plugin.
+ */
+const QTX_SLUGS_LEGACY_QTS_META_PREFIX    = '_qts_slug_';
+const QTX_SLUGS_LEGACY_QTS_OPTIONS_PREFIX = '_qts_';
+const QTX_SLUGS_LEGACY_QTS_OPTIONS_NAME   = 'qts_options';
+
+/**
+ * Check if slugs meta should be migrated from the legacy QTS postmeta and termmeta.
+ *
+ * @return string messages giving details, empty if new meta found or no legacy meta found.
+ */
+function qtranxf_slugs_check_migrate_qts() {
+    global $wpdb;
+
+    /**
+     * Generic function that counts the slugs meta, legacy (QTS) or new (QTX).
+     *
+     * @param string $table name of the meta table (postmeta, termmeta)
+     * @param string $prefix prefix for the meta key
+     * @param string[] $msg array of messages, updated
+     *
+     * @return void
+     */
+    $count_slugs = function ( $table, $prefix, &$msg ) use ( $wpdb ) {
+        $results = $wpdb->get_var( "SELECT count(*) FROM  $table WHERE meta_key like '$prefix%'" );
+        if ( $results ) {
+            $msg[] = sprintf( __( "Found %d slugs from $table.", 'qtranslate' ), $results );
+        }
+    };
+
+    $msg = [];
+    $count_slugs( $wpdb->postmeta, QTX_SLUGS_META_PREFIX, $msg );
+    $count_slugs( $wpdb->termmeta, QTX_SLUGS_META_PREFIX, $msg );
+    if ( ! empty( $msg ) ) {
+        // Found some post/term meta with the new keys, no migrate to suggest (it can still be done manually).
+        return '';
+    }
+
+    $msg = [];
+    $count_slugs( $wpdb->postmeta, QTX_SLUGS_LEGACY_QTS_META_PREFIX, $msg );
+    $count_slugs( $wpdb->termmeta, QTX_SLUGS_LEGACY_QTS_META_PREFIX, $msg );
+
+    return empty ( $msg ) ? $msg : implode( '<br>', $msg );
+}
+
+/**
+ * Migrate slugs meta by migrating the legacy QTS postmeta and termmeta to QTX.
+ * Attention: current slugs meta are deleted if QTS slugs are found.
+ *
+ * @param bool $db_commit true to commit changes, false for dry-run mode.
+ *
+ * @return string messages giving details.
+ */
+function qtranxf_slugs_migrate_qts_meta( $db_commit ) {
+    global $wpdb;
+
+    $new_prefix = QTX_SLUGS_META_PREFIX;
+    $old_prefix = QTX_SLUGS_LEGACY_QTS_META_PREFIX;
+
+    /**
+     * Generic function that migrates QTS meta to QTX meta.
+     *
+     * @param string $table name of the meta table (postmeta, termmeta)
+     * @param string $colid column name of the parent id (post_id, term_id)
+     * @param string[] $msg array of messages, updated
+     *
+     * @return void
+     */
+    $migrate_meta = function ( $table, $colid, $db_commit, &$msg ) use ( $wpdb, $old_prefix, $new_prefix ) {
+        $count_qts = $wpdb->get_var( "SELECT count(*) FROM  $table WHERE meta_key like '$old_prefix%'" );
+        if ( ! $count_qts ) {
+            $msg[] = sprintf( __( "No slugs to migrate from %s.", 'qtranslate' ), $table );
+
+            return;
+        }
+        // Find the related post_id/term_id to delete (not meta_id), to ensure the migrated slugs replace the whole existing groups.
+        $id_to_delete = "SELECT DISTINCT($colid) FROM $table WHERE meta_key LIKE '$old_prefix%'";
+        if ( $db_commit ) {
+            $results = $wpdb->query( "DELETE FROM $table WHERE meta_key like '$new_prefix%' AND $colid in ($id_to_delete)" );
+            $msg[]   = sprintf( __( "Deleted %d slugs from %s (%s).", 'qtranslate' ), $results ?: 0, $table, $new_prefix );
+            // Rename meta keys.
+            $results = $wpdb->query( "UPDATE $table SET meta_key = REPLACE(meta_key, '$old_prefix', '$new_prefix') WHERE meta_key LIKE '$old_prefix%'" );
+            $msg[]   = sprintf( __( "Migrated %d slugs from %s (%s).", 'qtranslate' ), $results ?: 0, $table, $old_prefix );
+        } else {
+            // Dry-run mode: show how many slugs are to be deleted and migrated, no change in DB.
+            $results = $wpdb->get_var( "SELECT count(*) FROM  $table WHERE meta_key like '$new_prefix%' AND $colid in ($id_to_delete)" );
+            $msg[]   = sprintf( __( "Deleted %d slugs from %s (%s).", 'qtranslate' ), $results ?: 0, $table, $new_prefix );
+            $msg[]   = sprintf( __( "Migrated %d slugs from %s (%s).", 'qtranslate' ), $count_qts, $table, $old_prefix );
+        }
+    };
+
+    $msg = [];
+    $migrate_meta( $wpdb->postmeta, 'post_id', $db_commit, $msg );
+    $migrate_meta( $wpdb->termmeta, 'term_id', $db_commit, $msg );
+
+    return implode( '<br>', $msg );
+}
+
+/**
+ * Migrate legacy QTS options to QTX.
+ * Attention: current slugs options are deleted if QTS options are found.
+ *
+ * @param bool $db_commit true to commit changes, false for dry-run mode.
+ *
+ * @return string messages giving details.
+ */
+function qtranxf_slugs_migrate_qts_options( $db_commit ) {
+    $msg = [];
+
+    $qts_options = get_option( QTX_SLUGS_LEGACY_QTS_OPTIONS_NAME );
+    if ( ! $qts_options ) {
+        return __( "No options to migrate.", 'qtranslate' );
+    }
+
+    $old_options = get_option( QTX_OPTIONS_MODULE_SLUGS );
+    if ( $old_options ) {
+        if ( $db_commit ) {
+            delete_option( QTX_OPTIONS_MODULE_SLUGS );
+        }
+        $msg[] = sprintf( __( "Deleted %d types from options.", 'qtranslate' ), count( $old_options ) );
+    }
+
+    $new_options = [];
+    // Drop the legacy prefix.
+    foreach ( $qts_options as $type => $slugs ) {
+        $type                 = str_replace( QTX_SLUGS_LEGACY_QTS_OPTIONS_PREFIX, '', $type );
+        $new_options[ $type ] = $slugs;
+    }
+    if ( $db_commit ) {
+        update_option( QTX_OPTIONS_MODULE_SLUGS, $new_options, false );
+        delete_option( QTX_SLUGS_LEGACY_QTS_OPTIONS_NAME );
+
+        global $qtranslate_slugs;
+        if ( $qtranslate_slugs->options_buffer != $new_options ) {
+            $qtranslate_slugs->options_buffer = $new_options;
+            flush_rewrite_rules();
+        }
+    }
+    $msg[] = sprintf( __( "Migrated %d types from options.", 'qtranslate' ), count( $new_options ) );
+
+    return implode( '<br/>', $msg );
+}
+
+/**
+ * Migrate slugs legacy QTS data (meta and options).
+ * Attention: current slugs data are deleted if QTS data are found.
+ *
+ * @param bool $db_commit true to commit changes, false for dry-run mode.
+ *
+ * @return string messages giving details.
+ */
+function qtranxf_slugs_migrate_qts_data( $db_commit ) {
+    $msg   = [];
+    $msg[] = $db_commit ? __( 'Migrate slugs:', 'qtranslate' ) : __( "Dry-run mode:", 'qtranslate' );
+    $msg[] = qtranxf_slugs_migrate_qts_meta( $db_commit );
+    $msg[] = qtranxf_slugs_migrate_qts_options( $db_commit );
+
+    if ( $db_commit ) {
+        qtranxf_update_admin_notice( 'slugs-migrate', true );  // Hide the automatic admin notice.
+    }
+
+    return implode( '<br/>', $msg );
+}
diff --git a/modules/slugs/admin/slugs-settings.php b/modules/slugs/admin/slugs-settings.php
index aa5491bc..025c315a 100644
--- a/modules/slugs/admin/slugs-settings.php
+++ b/modules/slugs/admin/slugs-settings.php
@@ -68,7 +68,7 @@ function qts_show_form_field( $args = array() ) {
         case 'text':
             $options[ $id ] = stripslashes( $options[ $id ] );
             $options[ $id ] = esc_attr( $options[ $id ] );
-            echo "<input class='regular-text$field_class' type='text' id='$id' name='" . QTX_OPTIONS_MODULE_SLUGS . "[$id]' value='$options[$id]' />";
+            echo "<input class='regular-text$field_class' type='text' name='" . QTX_OPTIONS_MODULE_SLUGS . "[$id]' value='$options[$id]' />";
             echo ( $desc != '' ) ? "<br /><p class='qtranxs-notes'>$desc</p>" : "";
             break;
 
@@ -93,7 +93,7 @@ function qts_show_form_field( $args = array() ) {
                 $name    = $q_config['language_name'][ $lang ];
                 $item_id = "$id|${item[1]}";
                 echo "<li><img class='qtranxs-lang-flag' src='${flag_location}${flag}' alt='$name' title='$name' />" . PHP_EOL;
-                echo "<input class='$field_class' type='text' id='$item_id' name='" . QTX_OPTIONS_MODULE_SLUGS . "[$item_id]' value='" . urldecode( $value ) . "' title='{$item[0]}' /></li>" . PHP_EOL;
+                echo "<input class='$field_class' type='text' name='" . QTX_OPTIONS_MODULE_SLUGS . "[$item_id]' value='" . urldecode( $value ) . "' title='{$item[0]}' /></li>" . PHP_EOL;
             }
             echo "</ul>";
             echo ( $desc != '' ) ? "<p class='qtranxs-notes'>$desc</p>" : "";
@@ -102,12 +102,12 @@ function qts_show_form_field( $args = array() ) {
         case 'textarea':
             $options[ $id ] = stripslashes( $options[ $id ] );
             $options[ $id ] = esc_html( $options[ $id ] );
-            echo "<textarea class='textarea$field_class' type='text' id='$id' name='" . QTX_OPTIONS_MODULE_SLUGS . "[$id]' rows='5' cols='30'>$options[$id]</textarea>";
+            echo "<textarea class='textarea$field_class' type='text' name='" . QTX_OPTIONS_MODULE_SLUGS . "[$id]' rows='5' cols='30'>$options[$id]</textarea>";
             echo ( $desc != '' ) ? "<br /><p class='qtranxs-notes'>$desc</p>" : "";
             break;
 
         case 'select':
-            echo "<select id='$id' class='select$field_class' name='" . QTX_OPTIONS_MODULE_SLUGS . "[$id]'>";
+            echo "<select class='select$field_class' name='" . QTX_OPTIONS_MODULE_SLUGS . "[$id]'>";
             foreach ( $choices as $item ) {
                 $value = esc_attr( $item );
                 $item  = esc_html( $item );
@@ -120,7 +120,7 @@ function qts_show_form_field( $args = array() ) {
             break;
 
         case 'select2':
-            echo "<select id='$id' class='select$field_class' name='" . QTX_OPTIONS_MODULE_SLUGS . "[$id]'>";
+            echo "<select class='select$field_class' name='" . QTX_OPTIONS_MODULE_SLUGS . "[$id]'>";
             foreach ( $choices as $item ) {
 
                 $item    = explode( "|", $item );
@@ -134,7 +134,7 @@ function qts_show_form_field( $args = array() ) {
             break;
 
         case 'checkbox':
-            echo "<input class='checkbox$field_class' type='checkbox' id='$id' name='" . QTX_OPTIONS_MODULE_SLUGS . "[$id]' value='1' " . checked( $options[ $id ], 1, false ) . " />";
+            echo "<input class='checkbox$field_class' type='checkbox' name='" . QTX_OPTIONS_MODULE_SLUGS . "[$id]' value='1' " . checked( $options[ $id ], 1, false ) . " />";
             echo ( $desc != '' ) ? "<br /><p class='qtranxs-notes'>$desc</p>" : "";
             break;
 
@@ -152,7 +152,7 @@ function qts_show_form_field( $args = array() ) {
                     }
                 }
 
-                echo "<input class='checkbox$field_class' type='checkbox' id='$id|$item[1]' name='" . QTX_OPTIONS_MODULE_SLUGS . "[$id|$item[1]]' value='1' $checked /> $item[0] <br/>";
+                echo "<input class='checkbox$field_class' type='checkbox' name='" . QTX_OPTIONS_MODULE_SLUGS . "[$id|$item[1]]' value='1' $checked /> $item[0] <br/>";
             }
             echo ( $desc != '' ) ? "<br /><p class='qtranxs-notes'>$desc</p>" : "";
             break;
@@ -170,7 +170,7 @@ function qts_show_form_field( $args = array() ) {
                     $checked = 'checked="checked"';
                 }
 
-                echo "<label for='$id|$item_value'><input class='radio$field_class' type='radio' id='$id|$item_value' name='" . QTX_OPTIONS_MODULE_SLUGS . "[$id]' value='$item_value' $checked /> <strong>$item_key</strong>";
+                echo "<label for='qtx_slugs_$id'><input class='radio$field_class' type='radio' id='qtx_slugs_$id' name='" . QTX_OPTIONS_MODULE_SLUGS . "[$id]' value='$item_value' $checked /> <strong>$item_key</strong>";
                 if ( isset( $desc[ $index ] ) && ! empty( $desc[ $index ] ) ) {
                     echo ": " . $desc[ $index ];
                 }
@@ -428,7 +428,7 @@ function qts_options_page_build_slug_fields( $object, $target_section, $id_prefi
 
     return array(
         "section" => $target_section,
-        "id"      => QTS_PREFIX . $id_prefix . $object->name,
+        "id"      => $id_prefix . $object->name,
         "title"   => qtranxf_use( qtranxf_getLanguage(), $object->label ),
         "desc"    => sprintf( '<code>https://example.org/<u>%s</u>/some-%s/</code>', $slug, $object->name ),
         'class'   => 'qts-slug', // used in qts_validate_options. TODO: cleaner way to be considered...
diff --git a/modules/slugs/slugs.php b/modules/slugs/slugs.php
index 38317db9..0a031fb1 100644
--- a/modules/slugs/slugs.php
+++ b/modules/slugs/slugs.php
@@ -1,11 +1,5 @@
 <?php
-
-if ( ! defined( "QTS_PREFIX" ) ) {
-    define( "QTS_PREFIX", '_qts_' );
-}
-if ( ! defined( "QTS_META_PREFIX" ) ) {
-    define( "QTS_META_PREFIX", QTS_PREFIX . 'slug_' );
-}
+const QTX_SLUGS_META_PREFIX = 'qtranslate_slug_';   // The language code is appended.
 
 include_once( dirname( __FILE__ ) . '/src/slugs-class-slugs.php' );
 include_once( dirname( __FILE__ ) . '/src/slugs-utils.php' );
diff --git a/modules/slugs/src/slugs-class-slugs.php b/modules/slugs/src/slugs-class-slugs.php
index d2b4bcd6..95f5a159 100644
--- a/modules/slugs/src/slugs-class-slugs.php
+++ b/modules/slugs/src/slugs-class-slugs.php
@@ -37,10 +37,6 @@ function init() {
             return;
         }
 
-        // TODO: remove temporary import of legacy option for master, rely on plugin activation in next release.
-        require_once( QTRANSLATE_DIR . '/admin/qtx_admin_options.php' );
-        qtranxf_import_legacy_option( 'qts_options', QTX_OPTIONS_MODULE_SLUGS, false );
-
         $this->options_buffer      = get_option( QTX_OPTIONS_MODULE_SLUGS, array() );
         $this->permalink_structure = get_option( 'permalink_structure' );
 
@@ -121,7 +117,7 @@ public function qts_body_class( $classes ) {
      * @return string the slug or empty if not found
      */
     public function get_slug( $id, $lang ) {
-        $slugArray = get_post_meta( $id, QTS_META_PREFIX . $lang );
+        $slugArray = get_post_meta( $id, QTX_SLUGS_META_PREFIX . $lang );
 
         return ! empty( $slugArray ) ? $slugArray[0] : "";
     }
@@ -162,7 +158,7 @@ public function get_base_slug( $name = false, $lang = false ) {
             return false;
         }
         $qts_options = $this->options_buffer;
-        $option_name = QTS_PREFIX . $type . '_' . $name;
+        $option_name = $type . '_' . $name;
         if ( isset( $qts_options[ $option_name ][ $lang ] ) ) {
             return $qts_options[ $option_name ][ $lang ];
         }
@@ -603,7 +599,7 @@ public function post_type_link( $link, $post, $leavename, $sample ) {
         $permastruct = $wp_rewrite->get_extra_permastruct( $post->post_type );
         $post_link   = $this->get_extra_permastruct( $permastruct, $post->post_type );
 
-        $slug = get_post_meta( $post->ID, QTS_META_PREFIX . $this->get_temp_lang(), true );
+        $slug = get_post_meta( $post->ID, QTX_SLUGS_META_PREFIX . $this->get_temp_lang(), true );
         if ( ! $slug ) {
             $slug = $post->post_name;
         }
@@ -681,7 +677,7 @@ public function post_link( $link, $post, $leavename ) {
                 if ( $cats ) {
                     usort( $cats, '_usort_terms_by_ID' ); // order by ID
 
-                    $category = get_metadata( 'term', $cats[0]->term_id, QTS_META_PREFIX . $this->get_temp_lang(), true );
+                    $category = get_metadata( 'term', $cats[0]->term_id, QTX_SLUGS_META_PREFIX . $this->get_temp_lang(), true );
                     if ( ! $category ) {
                         $category = $cats[0]->slug;
                     }
@@ -695,7 +691,7 @@ public function post_link( $link, $post, $leavename ) {
                 if ( empty( $category ) ) {
                     $default_category = get_category( get_option( 'default_category' ) );
 
-                    $default_category_slug = get_metadata( 'term', $default_category->term_id, QTS_META_PREFIX . $this->get_temp_lang(), true );
+                    $default_category_slug = get_metadata( 'term', $default_category->term_id, QTX_SLUGS_META_PREFIX . $this->get_temp_lang(), true );
                     if ( ! $default_category_slug ) {
                         $default_category_slug = $default_category->slug;
                     }
@@ -712,7 +708,7 @@ public function post_link( $link, $post, $leavename ) {
 
             $date = explode( " ", date( 'Y m d H i s', $unixtime ) );
 
-            $post_slug = get_post_meta( $post->ID, QTS_META_PREFIX . $this->get_temp_lang(), true );
+            $post_slug = get_post_meta( $post->ID, QTX_SLUGS_META_PREFIX . $this->get_temp_lang(), true );
             if ( ! $post_slug ) {
                 $post_slug = $post->post_name;
             }
@@ -822,7 +818,7 @@ public function term_link( $link, $term, $taxonomy ) {
         $permastruct = $wp_rewrite->get_extra_permastruct( $taxonomy );
         $termlink    = $this->get_extra_permastruct( $permastruct, $taxonomy );
 
-        $slug = get_metadata( 'term', $term->term_id, QTS_META_PREFIX . $this->get_temp_lang(), true );
+        $slug = get_metadata( 'term', $term->term_id, QTX_SLUGS_META_PREFIX . $this->get_temp_lang(), true );
         if ( ! $slug ) {
             $slug = $term->slug;
         }
@@ -845,7 +841,7 @@ public function term_link( $link, $term, $taxonomy ) {
                 foreach ( $ancestors as $ancestor ) {
                     $ancestor_term = get_term( $ancestor, $taxonomy );
 
-                    $ancestor_slug = get_metadata( 'term', $ancestor_term->term_id, QTS_META_PREFIX . $this->get_temp_lang(), true );
+                    $ancestor_slug = get_metadata( 'term', $ancestor_term->term_id, QTX_SLUGS_META_PREFIX . $this->get_temp_lang(), true );
                     if ( ! $ancestor_slug ) {
                         $ancestor_slug = $ancestor_term->slug;
                     }
@@ -983,7 +979,7 @@ private function get_page_id_by_path( $page_path, $post_type = 'page' ) {
         },
             $parts );
         $in_string     = "'" . implode( "','", $parts ) . "'";
-        $meta_key      = QTS_META_PREFIX . $this->get_temp_lang();
+        $meta_key      = QTX_SLUGS_META_PREFIX . $this->get_temp_lang();
         $post_type_sql = $post_type;
         $wpdb->escape_by_ref( $post_type_sql );
 
@@ -1097,7 +1093,7 @@ private function get_category_parents( $id, $link = false, $separator = '/', $ni
         }
 
         if ( $nicename ) {
-            $name = get_metadata( 'term', $parent->term_id, QTS_META_PREFIX . $this->get_temp_lang(), true );
+            $name = get_metadata( 'term', $parent->term_id, QTX_SLUGS_META_PREFIX . $this->get_temp_lang(), true );
             if ( ! $name ) {
                 $name = $parent->slug;
             }
@@ -1133,7 +1129,7 @@ private function get_page_uri( $page ) {
             $page = get_post( $page );
         }
 
-        $uri = get_post_meta( $page->ID, QTS_META_PREFIX . $this->get_temp_lang(), true );
+        $uri = get_post_meta( $page->ID, QTX_SLUGS_META_PREFIX . $this->get_temp_lang(), true );
         if ( ! $uri ) {
             $uri = $page->post_name;
         }
@@ -1146,7 +1142,7 @@ private function get_page_uri( $page ) {
         while ( $page->post_parent != 0 ) {
             $page = get_post( $page->post_parent );
 
-            $page_name = get_post_meta( $page->ID, QTS_META_PREFIX . $this->get_temp_lang(), true );
+            $page_name = get_post_meta( $page->ID, QTX_SLUGS_META_PREFIX . $this->get_temp_lang(), true );
             if ( ! $page_name ) {
                 $page_name = $page->post_name;
             }
@@ -1176,7 +1172,7 @@ private function get_term_by( $field, $value, $taxonomy ) {
         $original_field = $field;
 
         if ( 'slug' == $field ) {
-            $field = 'm.meta_key = \'' . QTS_META_PREFIX . $this->get_temp_lang() . '\' AND m.meta_value';
+            $field = 'm.meta_key = \'' . QTX_SLUGS_META_PREFIX . $this->get_temp_lang() . '\' AND m.meta_value';
             $value = sanitize_title( $value );
             if ( empty( $value ) ) {
                 return false;