There may be not any totally free addon for putting in Google Tag Manager in PrestaShop except purchasing a paid addon. Prestashop also doesn’t give use of Web site code so we can easily incorporate Tag Manager code but there is still an alternate way by right modifying the web https://addons.prestashop.com/en/seo-natural-search-engine-optimization/30904-automatic-hreflang-tags-canonical-tags-all-pages-seo.html