I selected the website’s header template that is situated at /themes/traditional/templates/_partials/header.tpl. With the help of your hook h = ‘MyCustomNameHooks’ Probably another person have created it with GTM ? It's realy wonderful tool, but it surely have to be inserted just after opening tag in all pages. Also see this https://bookmarksystem.com/story18651069/the-5-second-trick-for-prestashop-canonical-url