MediaWiki:Apihelp-query+imageinfo-paramvalue-prop-extmetadata
From Nasqueron Agora
Lists formatted metadata combined from multiple sources. Results are HTML formatted. If the file has been revision deleted, a filehidden property will be returned.
Note: This is an expensive property to request, and should be avoided unless you need it. When using it, you should request only a few results at a time to avoid too much load.
