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    HTML microdata, an HTML5 specification, is used to label content to describe a specific type of information. It is machine-readable data that is embedded in HTML documents and compatible with other data formats, including RDF and JSON. The purpose of the microdata specification is to help automated programs to better understand the content of your web page.

    Microdata Item Types and Properties

    Microdata could include information types such as reviews, personal information or events. Each information type has its own properties. For example properties of an event include venue, starting time, name, and category. Microdata is implemented using attributes in HTML tags, typically or is used to assign descriptive names to properties.

    The basic syntax for HTML microdata consists of a group of name-value pairs. The groups are called items, and each name-value pair is a property. The HTML microdata specification defines five attributes that can be applied to any HTML5 tag:

    • Itemscope: Indicates the element is a microdata element and its child elements are part of its microdata format.
    • Itemtype: Defines the vocabulary to be used by the microdata format.
    • Itemid: The unique identifier of the item, if defined by the microdata vocabulary.
    • Itemprop: An individual data element.
    • Itemref: Allows a microdata element to reference another element on the page to define it by either HTML id or by itemid.

    Recommended Reading: Learn more about the five attributes in this Web Developer Tutorial.

    The W3C HTML Microdata Specification

    The syntax and code examples are available in the W3C HTML Microdata specification. The W3C HTML Working Group is the W3C working group responsible for the HTML microdata specification.