Microdata (HTML)

Microdata vocabularies do not provide the semantics, or meaning of an Item.[11] Web developers can design a custom vocabulary or use vocabularies available on the web. A collection of commonly used markup vocabularies are provided by Schema.org schemas which include: Person, "Place", Event, Organization, Product, Review, Review-aggregate, Breadcrumb, Offer, Offer-aggregate. The website schema.org was established by search engine operators like Google, Microsoft, Yahoo!, and Yandex, which use microdata markup to improve search results.[12]^:85

For some purposes, an ad-hoc vocabulary is adequate. For others, a vocabulary will need to be designed. Where possible, authors are encouraged to re-use existing vocabularies, as this makes content re-use easier.[1]

In some cases, search engines covering specific regions may provide locally-specific extensions of microdata. For example, Yandex, a major search engine in Russia, supports microformats such as hCard (company contact information), hRecipe (food recipe), hReview (market reviews) and hProduct (product data) and provides its own format for definition of the terms and encyclopedic articles. This extension was made in order to solve transliteration problems between the Cyrillic and Latin alphabets. After the implementation of additional parameters from Schema's vocabulary,[13] indexation of information in Russian-language web-pages became more successful.

• itemscope – Creates the Item and indicates that descendants of this element contain information about it.[1]
• itemtype – A valid URL of a vocabulary that describes the item and its properties context.
• itemid – Indicates a unique identifier of the item.
• itemprop – Indicates that its containing tag holds the value of the specified item property. The property's name and value context are described by the item's vocabulary. Properties values usually consist of string values, but can also use URLs using the a element and its href attribute, the img element and its src attribute, or other elements that link to or embed external resources.[1]
• itemref – Properties that are not descendants of the element with the itemscope attribute can be associated with the item using this attribute. Provides a list of element ids (not itemids) with additional properties elsewhere in the document.[1]
• datetime - Indicates date or duration as specified by ISO 8601 standard.

The following HTML5 markup may be found on a typical “About” page containing information about a person:

<section> Hello, my name is John Doe, I am a graduate research assistant at
the University of Dreams.
My friends call me Johnny. 
You can visit my homepage at <a href="http://www.JohnnyD.com">www.JohnnyD.com</a>.
I live at 1234 Peach Drive, Warner Robins, Georgia.</section>

Here is the same markup with added Schema.org[14][15][16] Microdata:

<section itemscope itemtype="http://schema.org/Person"> 
	Hello, my name is 
	<span itemprop="name">John Doe</span>, 
	I am a 
	<span itemprop="jobTitle">graduate research assistant</span> 
	at the 
	<span itemprop="affiliation">University of Dreams</span>. 
	My friends call me 
	<span itemprop="additionalName">Johnny</span>. 
	You can visit my homepage at 
	<a href="http://www.JohnnyD.com" itemprop="url">www.JohnnyD.com</a>. 
	<section itemprop="address" itemscope itemtype="http://schema.org/PostalAddress">
		I live at 
		<span itemprop="streetAddress">1234 Peach Drive</span>,
		<span itemprop="addressLocality">Warner Robins</span>,
		<span itemprop="addressRegion">Georgia</span>.
	</section>
</section>

As the above example shows, Microdata items can be nested. In this case, an item of type http://schema.org/PostalAddress is nested inside an item of type http://schema.org/Person.

The following text shows how Google parses the Microdata from the above example code. Developers can test pages containing Microdata using Google's Rich Snippet Testing Tool.[17]

Item
   Type: http://schema.org/Person
   name = John Doe
   jobTitle = graduate research assistant
   affiliation = University of Dreams
   additionalName = Johnny
   url = http://www.johnnyd.com/
   address = Item(1)
Item 1
   Type: http://schema.org/PostalAddress
   streetAddress = 1234 Peach Drive
   addressLocality = Warner Robins
   addressRegion = Georgia

The same machine-readable terms can be used not only in HTML Microdata, but also in other annotations such as RDFa or JSON-LD in the markup, or in an external RDF file in a serialization such as RDF/XML, Notation3, or Turtle.

• Servers: Google can[18] use microdata in its result pages.[17] It is the preferred snippet format for the Google+ social network.[19]
• Browsers: As of December 2013, notable browsers that added support for the Microdata DOM API, are.[20] As of April 2018, Microdata DOM API is deprecated according to Mozilla.[21]

• Libraries: MicrodataJS[23] is a JavaScript library and jQuery plugin that emulates the DOM API.

• Semantic web
• Microformat
• RDFa Lite
• JSON-LD
• Semantic HTML
• Semantic social network

• Microdata — HTML Draft Standard, WHATWG
• W3C HTML Microdata Working Group Note, W3C
• Almaer, Dion (2009-05-11), Hixie discusses the addition of HTML5 "microdata", Ajaxian
• HTML5 Microdata Specs, Data-Vocabulary.org