There's various bugs open for different implementations of sharing protocols, such as:
* Schema.org - https://schema.org/
** {T106650}
** {T106651}
** E.g. Google+ structured data - https://developers.google.com/search/docs/guides/intro-structured-data
* Open Graph - http://opengraphprotocol.org/
** {T51859}
** {T33338}
** E.g. Facebook Open Graph - https://developers.facebook.com/docs/opengraph/
** https://www.mediawiki.org/wiki/Extension:WikiSEO exists
* ?
** {T32113}
** {T101711}
* Twitter Cards - https://dev.twitter.com/docs/cards
** lowest priority, per extensive discussion in {T64811}
** plus twitter uses Open Graph as a fallback for the 3 main items, cf. https://dev.twitter.com/cards/markup
There are also various issues with either implementations of those, or general problems to solve in this area.
**See also:**
* https://www.mediawiki.org/wiki/Extension:HTML_Tags (no phabricator project)
* https://www.mediawiki.org/wiki/Extension:OpenGraphMeta (no phabricator project)
* Brief explanations of the differences between opengraph and schema.org: http://stackoverflow.com/questions/6402528/opengraph-or-schema-org )