You have probably seen search results that show more than a blue link and a snippet: a publish date, an author, or a breadcrumb trail of the site's hierarchy. These are called rich results, and the raw material behind them is structured data embedded in the page. This post covers JSON-LD, today's most common format: what it describes and how to verify it, using the implementation on this blog (wpmm.jp/blog and en.wpmm.jp/blog) as the example.

Note: structured data is an annotation that presents a page's meaning in a machine-readable form. Writing it does not guarantee any particular display. It is a hint that helps a search engine understand the content.

What Problem It Addresses

A person looking at a page can tell "this is an article, published on this date, by this author." A search engine has to infer that from markup and layout. Is a date-like string the publish date or the last-updated date? Is a name-like string the author or a quoted source?…