You specify the main URL as the search engine may have issues figuring out which just one should be the main URL.  The subsequent tutorial will show you tips on how to allow Canonical URLs in Prestashop 1.5. By default, PrestaShop's deep URLs (that's, unique pages as an alternative https://bookmarkpath.com/story19168903/top-guidelines-of-automatische-hreflang-tags-und-kanonische-tags-seo