the code Google expects for this language. The hreflang should contain at least the language code (usually, made of two letters), or, if you want to specify the country/region, it sould be the same information as the locale name, but in a slightly different format. If the locale for Canadian French is fr_CA, the corresponding hreflang would be fr-ca. Instead of an underscore, use a dash (-) and all letters should be lowercase.