itemid - Microdata Global Identifier

The `itemid` Attribute

Global Attribute HTML5

The itemid attribute provides a unique global identifier for a Microdata item. It allows you to specify a globally unique identifier for an item using standard identifier schemes like ISBN for books, GTIN for products, or URLs.

Quick Example

<!-- Book with ISBN identifier -->
<div itemscope itemtype="https://schema.org/Book"
   itemid="urn:isbn:978-0-596-52932-1">
<span itemprop="name">JavaScript: The Good Parts</span>
<span itemprop="author">Douglas Crockford</span>
<span itemprop="isbn">978-0-596-52932-1</span>
</div>

<!-- Product with URL identifier -->
<div itemscope itemtype="https://schema.org/Product"
   itemid="https://example.com/products/12345">
<span itemprop="name">Wireless Headphones</span>
<span itemprop="sku">WH-12345</span>
</div>

<style>
div[itemscope] {
  padding: 15px;
  margin: 10px 0;
  border: 2px solid #e2e8f0;
  border-radius: 6px;
  background: #f8fafc;
}
span {
  display: block;
  margin: 5px 0;
}
span[itemprop="name"] {
  font-weight: bold;
  color: #1e40af;
  font-size: 1.1em;
}
</style>

Result

Interactive code playground requires JavaScript. Here's the code:

<!-- Book with ISBN identifier -->
<div itemscope itemtype="https://schema.org/Book"
   itemid="urn:isbn:978-0-596-52932-1">
<span itemprop="name">JavaScript: The Good Parts</span>
<span itemprop="author">Douglas Crockford</span>
<span itemprop="isbn">978-0-596-52932-1</span>
</div>

<!-- Product with URL identifier -->
<div itemscope itemtype="https://schema.org/Product"
   itemid="https://example.com/products/12345">
<span itemprop="name">Wireless Headphones</span>
<span itemprop="sku">WH-12345</span>
</div>

<style>
div[itemscope] {
  padding: 15px;
  margin: 10px 0;
  border: 2px solid #e2e8f0;
  border-radius: 6px;
  background: #f8fafc;
}
span {
  display: block;
  margin: 5px 0;
}
span[itemprop="name"] {
  font-weight: bold;
  color: #1e40af;
  font-size: 1.1em;
}
</style>

Syntax

<element itemscope itemtype="type-url" itemid="identifier">
  <!-- Item properties -->
</element>

When to Use itemid

Use the itemid attribute when marking up items that have globally unique identifiers recognized by standard schemes:

Books and Publications

Use ISBN (International Standard Book Number) for books and publications:

<article itemscope
       itemtype="https://schema.org/Book"
       itemid="urn:isbn:978-1-491-91866-1">
<h3 itemprop="name">Learning Web Design</h3>
<div>
  <strong>Author:</strong>
  <span itemprop="author">Jennifer Robbins</span>
</div>
<div>
  <strong>ISBN:</strong>
  <span itemprop="isbn">978-1-491-91866-1</span>
</div>
<div>
  <strong>Publisher:</strong>
  <span itemprop="publisher">O'Reilly Media</span>
</div>
</article>

<style>
article {
  max-width: 400px;
  padding: 20px;
  border: 2px solid #3b82f6;
  border-radius: 8px;
  background: linear-gradient(to bottom, #eff6ff, #ffffff);
}
h3 {
  margin-top: 0;
  color: #1e40af;
}
div {
  margin: 8px 0;
}
strong {
  color: #475569;
}
</style>

Result

Interactive code playground requires JavaScript. Here's the code:

<article itemscope
       itemtype="https://schema.org/Book"
       itemid="urn:isbn:978-1-491-91866-1">
<h3 itemprop="name">Learning Web Design</h3>
<div>
  <strong>Author:</strong>
  <span itemprop="author">Jennifer Robbins</span>
</div>
<div>
  <strong>ISBN:</strong>
  <span itemprop="isbn">978-1-491-91866-1</span>
</div>
<div>
  <strong>Publisher:</strong>
  <span itemprop="publisher">O'Reilly Media</span>
</div>
</article>

<style>
article {
  max-width: 400px;
  padding: 20px;
  border: 2px solid #3b82f6;
  border-radius: 8px;
  background: linear-gradient(to bottom, #eff6ff, #ffffff);
}
h3 {
  margin-top: 0;
  color: #1e40af;
}
div {
  margin: 8px 0;
}
strong {
  color: #475569;
}
</style>

Products with GTIN/UPC

Use GTIN (Global Trade Item Number) or UPC for retail products:

<div itemscope
   itemtype="https://schema.org/Product"
   itemid="urn:gtin:00012345678905">
<h3 itemprop="name">Organic Coffee Beans</h3>
<div>
  <strong>Brand:</strong>
  <span itemprop="brand">Premium Roast</span>
</div>
<div>
  <strong>GTIN:</strong>
  <span itemprop="gtin">00012345678905</span>
</div>
<div>
  <strong>Price:</strong>
  <span itemprop="price">$14.99</span>
  <meta itemprop="priceCurrency" content="USD">
</div>
</div>

<style>
div[itemscope] {
  max-width: 350px;
  padding: 18px;
  border: 2px solid #059669;
  border-radius: 8px;
  background: linear-gradient(to bottom, #ecfdf5, #ffffff);
}
h3 {
  margin-top: 0;
  color: #047857;
}
div[itemscope] > div {
  margin: 8px 0;
}
strong {
  color: #475569;
}
</style>

Result

Interactive code playground requires JavaScript. Here's the code:

<div itemscope
   itemtype="https://schema.org/Product"
   itemid="urn:gtin:00012345678905">
<h3 itemprop="name">Organic Coffee Beans</h3>
<div>
  <strong>Brand:</strong>
  <span itemprop="brand">Premium Roast</span>
</div>
<div>
  <strong>GTIN:</strong>
  <span itemprop="gtin">00012345678905</span>
</div>
<div>
  <strong>Price:</strong>
  <span itemprop="price">$14.99</span>
  <meta itemprop="priceCurrency" content="USD">
</div>
</div>

<style>
div[itemscope] {
  max-width: 350px;
  padding: 18px;
  border: 2px solid #059669;
  border-radius: 8px;
  background: linear-gradient(to bottom, #ecfdf5, #ffffff);
}
h3 {
  margin-top: 0;
  color: #047857;
}
div[itemscope] > div {
  margin: 8px 0;
}
strong {
  color: #475569;
}
</style>

URLs as Identifiers

Use URLs when the item has a canonical web address:

<div itemscope
   itemtype="https://schema.org/Person"
   itemid="https://example.com/people/jane-smith">
<h3 itemprop="name">Jane Smith</h3>
<div>
  <strong>Job Title:</strong>
  <span itemprop="jobTitle">Senior Software Engineer</span>
</div>
<div>
  <strong>Email:</strong>
  <a itemprop="email" href="mailto:jane@example.com">
    jane@example.com
  </a>
</div>
<div>
  <strong>Profile URL:</strong>
  <a itemprop="url" href="https://example.com/people/jane-smith">
    View Profile
  </a>
</div>
</div>

<style>
div[itemscope] {
  max-width: 400px;
  padding: 20px;
  border: 2px solid #8b5cf6;
  border-radius: 8px;
  background: linear-gradient(to bottom, #f5f3ff, #ffffff);
}
h3 {
  margin-top: 0;
  color: #6d28d9;
}
div[itemscope] > div {
  margin: 8px 0;
}
strong {
  color: #475569;
}
a {
  color: #7c3aed;
  text-decoration: none;
}
a:hover {
  text-decoration: underline;
}
</style>

Result

Interactive code playground requires JavaScript. Here's the code:

<div itemscope
   itemtype="https://schema.org/Person"
   itemid="https://example.com/people/jane-smith">
<h3 itemprop="name">Jane Smith</h3>
<div>
  <strong>Job Title:</strong>
  <span itemprop="jobTitle">Senior Software Engineer</span>
</div>
<div>
  <strong>Email:</strong>
  <a itemprop="email" href="mailto:jane@example.com">
    jane@example.com
  </a>
</div>
<div>
  <strong>Profile URL:</strong>
  <a itemprop="url" href="https://example.com/people/jane-smith">
    View Profile
  </a>
</div>
</div>

<style>
div[itemscope] {
  max-width: 400px;
  padding: 20px;
  border: 2px solid #8b5cf6;
  border-radius: 8px;
  background: linear-gradient(to bottom, #f5f3ff, #ffffff);
}
h3 {
  margin-top: 0;
  color: #6d28d9;
}
div[itemscope] > div {
  margin: 8px 0;
}
strong {
  color: #475569;
}
a {
  color: #7c3aed;
  text-decoration: none;
}
a:hover {
  text-decoration: underline;
}
</style>

Common Identifier Schemes

ISBN for Books

The International Standard Book Number is a unique numeric commercial book identifier:

<!-- Using URN format -->
<div itemscope
     itemtype="https://schema.org/Book"
     itemid="urn:isbn:978-0-545-01022-1">
  <span itemprop="name">Harry Potter and the Deathly Hallows</span>
</div>

<!-- Or using URL format -->
<div itemscope
     itemtype="https://schema.org/Book"
     itemid="https://www.worldcat.org/isbn/9780545010221">
  <span itemprop="name">Harry Potter and the Deathly Hallows</span>
</div>

GTIN/UPC for Products

Global Trade Item Numbers identify products worldwide:

<!-- GTIN-13 (EAN) -->
<div itemscope
     itemtype="https://schema.org/Product"
     itemid="urn:gtin:5012345678900">
  <span itemprop="name">Product Name</span>
</div>

<!-- UPC (GTIN-12) -->
<div itemscope
     itemtype="https://schema.org/Product"
     itemid="urn:gtin:012345678905">
  <span itemprop="name">Product Name</span>
</div>

DOI for Academic Papers

Digital Object Identifiers for scholarly articles and research:

<article itemscope
         itemtype="https://schema.org/ScholarlyArticle"
         itemid="https://doi.org/10.1000/182">
  <h2 itemprop="headline">
    The Impact of Climate Change on Ecosystems
  </h2>
  <span itemprop="author">Dr. Sarah Johnson</span>
</article>

Custom URN Schemes

You can use custom URN schemes for internal or domain-specific identifiers:

<div itemscope
     itemtype="https://schema.org/Organization"
     itemid="urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6">
  <span itemprop="name">Acme Corporation</span>
</div>

Difference Between itemid and id

The itemid and id attributes serve different purposes:

itemid Attribute
id Attribute

Purpose: Global identifier for Microdata items

Scope: Must be globally unique across the web

Format: Must be a URL or URN

Usage: For structured data consumed by search engines and tools

<div itemscope
     itemtype="https://schema.org/Book"
     itemid="urn:isbn:978-0-262-03384-8">
  <span itemprop="name">
    Introduction to Algorithms
  </span>
</div>

Purpose: Unique identifier within a single HTML document

Scope: Must be unique only within the current page

Format: Any string without spaces (case-sensitive)

Usage: For CSS styling, JavaScript, and page navigation

<div id="book-section">
  <h2>Featured Books</h2>
  <p>Check out our collection...</p>
</div>

<style>
  #book-section {
    padding: 20px;
    background: #f3f4f6;
  }
</style>

Complete Example

<article id="featured-book"
       itemscope
       itemtype="https://schema.org/Book"
       itemid="urn:isbn:978-0-13-468599-1">
<header>
  <h2 itemprop="name">
    The Pragmatic Programmer
  </h2>
  <p class="subtitle">
    Your Journey to Mastery
  </p>
</header>

<div class="details">
  <div class="detail-row">
    <strong>Authors:</strong>
    <span itemprop="author">David Thomas</span>,
    <span itemprop="author">Andrew Hunt</span>
  </div>

  <div class="detail-row">
    <strong>ISBN:</strong>
    <span itemprop="isbn">978-0-13-468599-1</span>
  </div>

  <div class="detail-row">
    <strong>Publisher:</strong>
    <span itemprop="publisher">Addison-Wesley</span>
  </div>

  <div class="detail-row">
    <strong>Published:</strong>
    <time itemprop="datePublished" datetime="2019-09-13">
      September 13, 2019
    </time>
  </div>
</div>

<div class="description">
  <strong>Description:</strong>
  <p itemprop="description">
    A comprehensive guide to software craftsmanship
    and best practices for professional developers.
  </p>
</div>
</article>

<style>
article {
  max-width: 600px;
  padding: 24px;
  border: 3px solid #2563eb;
  border-radius: 10px;
  background: linear-gradient(to bottom right, #eff6ff, #ffffff);
  box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

header {
  border-bottom: 2px solid #bfdbfe;
  padding-bottom: 12px;
  margin-bottom: 16px;
}

h2 {
  margin: 0 0 8px 0;
  color: #1e40af;
  font-size: 1.5em;
}

.subtitle {
  margin: 0;
  color: #64748b;
  font-style: italic;
}

.details {
  margin-bottom: 16px;
}

.detail-row {
  margin: 8px 0;
  padding: 8px;
  background: rgba(255, 255, 255, 0.7);
  border-radius: 4px;
}

strong {
  color: #334155;
  display: inline-block;
  min-width: 100px;
}

.description {
  margin-top: 16px;
  padding: 16px;
  background: rgba(37, 99, 235, 0.05);
  border-left: 4px solid #2563eb;
  border-radius: 4px;
}

.description strong {
  display: block;
  margin-bottom: 8px;
}

.description p {
  margin: 0;
  color: #475569;
  line-height: 1.6;
}
</style>

Result

Interactive code playground requires JavaScript. Here's the code:

<article id="featured-book"
       itemscope
       itemtype="https://schema.org/Book"
       itemid="urn:isbn:978-0-13-468599-1">
<header>
  <h2 itemprop="name">
    The Pragmatic Programmer
  </h2>
  <p class="subtitle">
    Your Journey to Mastery
  </p>
</header>

<div class="details">
  <div class="detail-row">
    <strong>Authors:</strong>
    <span itemprop="author">David Thomas</span>,
    <span itemprop="author">Andrew Hunt</span>
  </div>

  <div class="detail-row">
    <strong>ISBN:</strong>
    <span itemprop="isbn">978-0-13-468599-1</span>
  </div>

  <div class="detail-row">
    <strong>Publisher:</strong>
    <span itemprop="publisher">Addison-Wesley</span>
  </div>

  <div class="detail-row">
    <strong>Published:</strong>
    <time itemprop="datePublished" datetime="2019-09-13">
      September 13, 2019
    </time>
  </div>
</div>

<div class="description">
  <strong>Description:</strong>
  <p itemprop="description">
    A comprehensive guide to software craftsmanship
    and best practices for professional developers.
  </p>
</div>
</article>

<style>
article {
  max-width: 600px;
  padding: 24px;
  border: 3px solid #2563eb;
  border-radius: 10px;
  background: linear-gradient(to bottom right, #eff6ff, #ffffff);
  box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

header {
  border-bottom: 2px solid #bfdbfe;
  padding-bottom: 12px;
  margin-bottom: 16px;
}

h2 {
  margin: 0 0 8px 0;
  color: #1e40af;
  font-size: 1.5em;
}

.subtitle {
  margin: 0;
  color: #64748b;
  font-style: italic;
}

.details {
  margin-bottom: 16px;
}

.detail-row {
  margin: 8px 0;
  padding: 8px;
  background: rgba(255, 255, 255, 0.7);
  border-radius: 4px;
}

strong {
  color: #334155;
  display: inline-block;
  min-width: 100px;
}

.description {
  margin-top: 16px;
  padding: 16px;
  background: rgba(37, 99, 235, 0.05);
  border-left: 4px solid #2563eb;
  border-radius: 4px;
}

.description strong {
  display: block;
  margin-bottom: 8px;
}

.description p {
  margin: 0;
  color: #475569;
  line-height: 1.6;
}
</style>

Best Practices

Use Standard Identifier Schemes

Choose well-established identifier schemes appropriate for your content type:

<!-- Good: Using standard ISBN format -->
<div itemscope
     itemtype="https://schema.org/Book"
     itemid="urn:isbn:978-1-449-36830-3">

<!-- Good: Using DOI for research paper -->
<article itemscope
         itemtype="https://schema.org/ScholarlyArticle"
         itemid="https://doi.org/10.1038/nature12373">

<!-- Avoid: Using non-standard or unclear identifiers -->
<div itemscope itemtype="https://schema.org/Book"
     itemid="book123">

Only Use When Necessary

Not every item needs an itemid. Use it only for items with established global identifiers:

<!-- Good: Book has ISBN, use itemid -->
<div itemscope
     itemtype="https://schema.org/Book"
     itemid="urn:isbn:978-0-13-110362-7">

<!-- Good: Blog post without global ID, no itemid needed -->
<article itemscope itemtype="https://schema.org/BlogPosting">
  <h1 itemprop="headline">My Latest Blog Post</h1>
</article>

Ensure itemscope and itemtype

The itemid attribute requires both itemscope and itemtype to be present:

<!-- Correct: All three attributes present -->
<div itemscope
     itemtype="https://schema.org/Product"
     itemid="urn:gtin:00012345678905">

<!-- Invalid: Missing itemscope -->
<div itemtype="https://schema.org/Product"
     itemid="urn:gtin:00012345678905">

<!-- Invalid: Missing itemtype -->
<div itemscope itemid="urn:gtin:00012345678905">

Use Valid URL or URN Format

The identifier must be a properly formatted URL or URN:

<!-- Good: Valid URN -->
<div itemscope itemtype="https://schema.org/Book"
     itemid="urn:isbn:978-0-596-00048-9">

<!-- Good: Valid URL -->
<div itemscope itemtype="https://schema.org/Person"
     itemid="https://example.com/users/12345">

<!-- Invalid: Not a URL or URN -->
<div itemscope itemtype="https://schema.org/Book"
     itemid="some-book-title">

Browser Support

The itemid attribute is part of the HTML5 Microdata specification and is supported by all modern browsers.

Browser	Support
Chrome	Yes (since Chrome 8)
Firefox	Yes (since Firefox 6)
Safari	Yes (since Safari 5.1)
Edge	Yes (all versions)
Opera	Yes (since Opera 11)

itemscope

Creates a new Microdata item scope. Required for using itemid.

Learn about itemscope →

itemtype

Specifies the vocabulary URL for the item. Required for using itemid.

Learn about itemtype →

itemprop

Adds a property to a Microdata item with a name-value pair.

Learn about itemprop →

Specifications

HTML Living Standard - itemid attribute

Schema.org - Getting Started

Microdata - W3C

itemid - Microdata Global Identifier

The itemid Attribute

Quick Example

Syntax

When to Use itemid

Books and Publications

Products with GTIN/UPC

URLs as Identifiers

Common Identifier Schemes

ISBN for Books

GTIN/UPC for Products

DOI for Academic Papers

Custom URN Schemes

Difference Between itemid and id

Complete Example

Best Practices

Use Standard Identifier Schemes

Only Use When Necessary

Ensure itemscope and itemtype

Use Valid URL or URN Format

Browser Support

Related Attributes

Specifications

The `itemid` Attribute