You specify the key URL as the internet search engine can have difficulty analyzing which a single need to be the main URL.  The subsequent tutorial will show you how you can allow Canonical URLs in Prestashop 1.5. Increase the indexing of your Prestashop urls in Google. This module https://addons.prestashop.com/ru/seo-natural-search-engine-optimization/31857--rich-snippets-json-ld-opengraph-seo.html