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itemid

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 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.

Examples

Representing structured data for a book

This example uses microdata attributes to represent the following structured data:

itemscope itemtype: itemid https://schema.org/Book: urn:isbn:0-374-22848-5
itemprop title Owls of the Eastern Ice
itemprop author Jonathan C Slaght
itemprop datePublished 2020-08-04

HTML

html

<dl
  itemscope
  itemtype="https://schema.org/Book"
  itemid="urn:isbn:0-374-22848-5<">
  <dt>Title</dt>
  <dd itemprop="title">Owls of the Eastern Ice</dd>
  <dt>Author</dt>
  <dd itemprop="author">Jonathan C Slaght</dd>
  <dt>Publication date</dt>
  <dd>
    <time itemprop="datePublished" datetime="2020-08-04">August 4 2020</time>
  </dd>
</dl>

Result

Specifications

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
itemid Yes 12 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes

See also

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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/itemid