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The itemid global attribute is the unique, global identifier of an item. An itemid attribute can only be specified for an element that has both itemscope and itemtype attributes. Also, itemid can only be specified on elements that possess an itemscope attribute whose corresponding itemtype refers to or defines a vocabulary that supports global identifiers.

The exact meaning of an itemtype's global identifier is provided by the definition of that identifier within the specified vocabulary. The vocabulary defines whether several items with the same global identifier can coexist and, if so, how items with the same identifier are handled.

Note: The definition specifies that an itemid must be a URL.  However, the following example correctly illustrates that a URN may also be used. This inconsistency may reflect the incomplete nature of the Microdata specification.



<dl itemscope
<dt>Title <dd itemprop="title">The Reality Dysfunction
<dt>Author <dd itemprop="author">Peter F. Hamilton
<dt>Publication date
<dd><time itemprop="pubdate" datetime="1996-01-26">26 January 1996</time> </dl>

Structured data

itemscope itemtype: itemid urn:isbn:0-330-34032-8
itemprop title The Reality Dysfunction
itemprop author
Peter F. Hamilton
itemprop pubdate 1996-01-26



Specification Status Comment
itemid   WG Note - No longer being actively developed

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support (Yes) (Yes) (Yes) (Yes) (Yes)
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support (Yes) (Yes) (Yes) (Yes) (Yes) (Yes)

See also

Document Tags and Contributors

 Contributors to this page: jeremy-french, SphinxKnight, rohanmahajan, rolfedh, duncanmcdonald
 Last updated by: jeremy-french,