Microdata is a WHATWG HTML specification used to nest semantics within existing content on web pages. Search engines, web crawlers, and browsers can extract and process Microdata from a web page and use it to provide a richer browsing experience for users. Search engines benefit greatly from direct access to this structured data because it allows search engines to understand the information on web pages and provide more relevant results to users. Microdata uses a supporting vocabulary to describe an item and name-value pairs to assign values to its properties. Microdata is an attempt to provide a simpler way of annotating HTML elements with machine-readable tags than the similar approaches of using RDFa and Microformats.
Microdata vocabularies provide the semantics, or meaning of an Item. 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, Event, Organization, Product, Review, Review-aggregate, Breadcrumb, Offer, Offer-aggregate. Major search engine operators like Google, Microsoft and Yahoo! rely on this markup to improve search results. 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.
Microdata global attributes
itemscope – Creates the Item and indicates that descendants of this element contain information about it.
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 properties name and value context are described by the items 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.
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.
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 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>
<span itemprop="affiliation">University of Dreams</span>.
My friends call me
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>,
As the above example shows, Microdata items can be nested. In this case an item of type http://schema.org/Address 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.
name = John Doe
jobTitle = graduate research assistant
affiliation = University of Dreams
additionalName = Johnny
url = http://www.johnnyd.com/
address = Item(1)
streetAddress = 1234 Peach Drive
addressLocality = Warner Robins
addressRegion = Georgia