og:locale
Declares the language and territory of the Open Graph object (e.g., en_US, fr_FR).
og:locale specifies the language and country of the page content using locale codes (language_TERRITORY format with underscores, not hyphens). The default if omitted is en_US. This is used by Facebook and some other platforms to serve content in the correct language context.
og:locale:alternate can specify alternate locale versions of the same content: <meta property="og:locale:alternate" content="fr_FR">. This is the Open Graph equivalent of hreflang — it tells Facebook that alternate versions exist in other locales.
For most English-language sites, og:locale="en_US" is fine. For multinational sites, set the correct locale on each language variant to help social platforms serve the right version to regional users.
HTML Example
<meta property="og:locale" content="en_US"> <!-- For sites with multilingual content: --> <meta property="og:locale:alternate" content="fr_FR"> <meta property="og:locale:alternate" content="de_DE">