The itemid global attribute provides microdata in the form of a 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 Whatwg.org 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.

Example

HTML

<dl itemscope
    itemtype="http://vocab.example.net/book"
    itemid="urn:isbn:0-330-34032-8">
<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
http://vocab.example.net/book: urn:isbn:0-330-34032-8
itemprop title The Reality Dysfunction
itemprop author
Peter F. Hamilton
itemprop pubdate 1996-01-26

Result

Specifications

Specification Status Comment
HTML Microdata
The definition of 'itemid' in that specification.
Working Draft  
HTML Living Standard
The definition of 'itemid' in that specification.
Living Standard  

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung Internet
Basic supportChrome Full support YesEdge Full support YesFirefox Full support YesIE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support YesOpera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yes

Legend

Full support  
Full support

See also

Document Tags and Contributors

Last updated by: mfuji09,