The og:url tag tells social networks which address a shared page lives at. When it differs from the canonical link, shares and search engines point at different URLs.
Why Joomla sites get it
Tags that build og:url from the address the visitor arrived on pick up every variation: the non-SEF URL, a different menu path, a query string, or the other host (with or without www.). There is a Joomla-specific cause too: the canonical host comes from the System – SEF plugin’s Site Domain when it is set, while other absolute URLs follow the site URL. If one of those includes www. and the other doesn’t, every page names two hosts.
Fix it by hand
- Make the Site Domain in the System – SEF plugin and your site URL (
$live_siteinconfiguration.php, if set) use the same host. - Make whatever writes your Open Graph tags use the canonical URL for
og:url.
Fix it with MetaGen
MetaGen writes og:url from the same canonical URL it puts in the canonical link, so the two always match. Its Canonical host agreement check shows which host your pages name and warns if the Site Domain and site URL disagree.
MetaGen is free for Joomla 5 and 6. See all the SEO warnings MetaGen checks.
