The hreflang “x-default” attribute benefit signals to Google algorithms the site doesn’t target any distinct language or locale and is particularly the default webpage when no other site is healthier suited. By default you should leave this attribute enabled, as disabling it affects all the stock management within your store. https://addons.prestashop.com/de/seo-suchmaschinenranking-optimization/30904-automatische-hreflang-tags-und-kanonische-tags-seo.html