Illustration: You have an e-commerce Web site with merchandise web pages for different sizes of a specific t-shirt.   You specify the main URL since the internet search engine can have issues determining which a single really should be the first URL.  The subsequent tutorial will show you the best https://www.presta-addons-modules.com/en/seo/prestashop-seo-automatic-hreflang-tags-canonical-tags-on-all-pages.html