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This page outlines the version 2.0 accessibility properties.

Version 2.0 adds accessMode, accessModeSufficient, and accessibilitySummary to the original 1.0 properties (accessibilityFeature, accessibilityHazard, accessibilityControl, and accessibilityAPI). These properties were incorporated into Schema.org version 3.2 on March 23, 2017.

An archive of the original 2.0 proposal is also available on this site.

See the a11ymetadata.org web site for information on how to get involved.

Vocabulary Naming Convention

The values defined in this vocabulary follow a camel-casing convention: single words are lowercase, while compound words are concatenated into a single value with a capital letter indicating the start of each connected word (e.g., "alternativeText"). This convention is not applied to acronyms, accessibility APIs and other values that already have recognized naming conventions (e.g., "MathML" and "iOSAccessibility").

To ensure maximum interoperability with user agents that process these properties, use the values exactly as they are defined in this vocabulary. Alternative case spellings may not be recognized (e.g., "mathml" or "aria").

User agent developers need to be aware that these values may not be strictly validated depending on the context in which they are created and used. Two values that differ only in case should be treated as identical.

Accessibility terms (Version 2.0)

Note: Many of the values described on this page were derived from the IMS Global Access for All (AfA) Information Model Data Element Specification, and there is more information there on some terms.

Property Expected Type Expected Values Description
accessibilityFeature Text
  • alternativeText
  • annotations
  • audioDescription
  • bookmarks
  • braille
  • captions
  • ChemML
  • describedMath
  • displayTransformability
  • highContrastAudio
  • highContrastDisplay
  • index
  • largePrint
  • latex
  • longDescription
  • MathML
  • none
  • printPageNumbers
  • readingOrder
  • rubyAnnotations
  • signLanguage
  • structuralNavigation
  • synchronizedAudioText
  • tableOfContents
  • taggedPDF
  • tactileGraphic
  • tactileObject
  • timingControl
  • transcript
  • ttsMarkup
  • unlocked
Content features of the resource, such as accessible media, supported enhancements for accessibility and alternatives.

See the accessibilityFeature in detail section below for more information.

accessibilityHazard Text
  • flashing
  • noFlashingHazard
  • motionSimulation
  • noMotionSimulationHazard
  • sound
  • noSoundHazard
  • unknown
  • none
A characteristic of the described resource that is physiologically dangerous to some users. Related to WCAG 2.0 guideline 2.3.

If none of the hazards are known to exist instead of calling out each nonHazard it is recommended to use "none". If the content has hazard(s), include positive assertions for the hazards it has and negative assertions for the others.

If the property is not set in the positive or negative or is specifically set to unknown, the state of hazards is not known.

See the accessibilityHazard in detail section below for more information.

accessibilityAPI Text
  • AndroidAccessibility
  • ARIA
  • ATK
  • AT-SPI
  • BlackberryAccessibility
  • iAccessible2
  • iOSAccessibility
  • JavaAccessibility
  • MacOSXAccessibility
  • MSAA
  • UIAutomation
Indicates that the resource is compatible with the referenced accessibility API.

See the accessibilityAPI in detail section below for more information.

accessibilityControl Text
  • fullKeyboardControl
  • fullMouseControl
  • fullSwitchControl
  • fullTouchControl
  • fullVideoControl
  • fullVoiceControl
Identifies one or more input methods that allow access to all of the application functionality.

See the accessibilityControl in detail section below for more information.

accessMode Text
  • auditory
  • chartOnVisual
  • chemOnVisual
  • colorDependent
  • diagramOnVisual
  • mathOnVisual
  • musicOnVisual
  • tactile
  • textOnVisual
  • textual
  • visual
The human sensory perceptual system or cognitive faculty through which a person may process or perceive information

See the accessMode in detail section below for more information.

accessModeSufficient Text
  • auditory
  • tactile
  • textual
  • visual
A list of single or combined accessModes that are sufficient to understand all the intellectual content of a resource

See the accessModeSufficient in detail section below for more information.

accessibilitySummary Text

Human readable summary of accessibility features and deficiencies

A human-readable summary of specific accessibility features or deficiencies, consistent with the other accessibility metadata but expressing subtleties such as "short descriptions are present but long descriptions will be needed for non-visual users" or "short descriptions are present and no long descriptions are needed."

See the accessibilitySummary in detail section below for more information.

accessibilityFeature in detail

schema.org's property definition of accessibilityFeature

The accessibilityFeature property supports many different values, and when alphabetized many of them will appear to have only tenuous relation. This section breaks the values out into their constituent groups to explain their inclusion.

There are four groups of features to be aware of:

  • Transform features identify characteristics of the content that can be manipulated by the user to make the content better fit their personal needs. The ability to change the font size of the text is one example of a transformation property.
  • Structure and navigation features identify navigation aids that are provided to simplify moving around within the media, such as the inclusion of a table of contents or an index.
  • Control features identify content and features that are fully controllable by the user. The ability to pause a timed interface is an example.
  • Augmentation features identify content features that provide alternate access to a resource. The inclusion of alternative text in an alt attribute is one of the most commonly identifiable augmentation features.

Each of the following section examines one of these classes values in more detail, listing the values and describing their expected use.

The property also includes the value "none" that can be set to indicate that the page has been checked but contains no special enhancements. The value can also be used to indicate that no statement about the accessibile nature of the content can be made. Setting this value helps differentiate pages that have been evaluated for accessibility from those that have not (i.e., to remove ambiguity about why the accessibilityFeature property might not have been set).

Features for transformation

Transform features either state how content is available in a transformed state or is set up so that a user can transform it. These properties derive from WCAG 2.0 section 1.4

Expected Values Description


Audio content with speech in the foreground meets the contrast thresholds set out in WCAG Success Criteria 1.4.7. The success criterion the audio meets can be appeneded, but is not required:
  • /noBackground - no background noise is present
  • /reducedBackground - at least 20db difference between foreground speech and background noise
  • /switchableBackground - background noise can be turned off (sufficient contrast may not be met without doing so)


Content meets the visual contrast threshold set out in WCAG Success Criteria 1.4.6.


The content has been formatted to meet large print guidelines. The specific point size may optionally be added as an extension (e.g., largePrint/18).

The property is not set if the font size can be increased. See displayTransformability.


Display properties are controllable by the user. This property can be set, for example, if custom CSS style sheets can be applied to the content to control the appearance. It can also be used to indicate that styling in document formats like Word and PDF can be modified.

This property can be modified to identify the specific display properties that allow meaningful control. Modifiers should take the form of CSS property names, even if CSS is not the document styling format:

  • /font-size
  • /font-family
  • /line-height
  • /word-spacing
  • /color
  • /background-color

Note that many CSS display properties can be modified, but not all usefully enhance the accessibility (e.g., image-based content).

Features for structure and navigation

The following values identify key navigation aids available with the work.

Expected Values Description


The work includes annotations from the author, instructor and/or others.


The work includes bookmarks to facilitate navigation to key points.


The work includes an index to the content.


The work includes equivalent print page numbers. This setting is most commonly used with ebooks for which there is a print equivalent.


The reading order of the content is clearly defined in the markup (e.g., figures, sidebars and other secondary content has been marked up to allow it to be skipped automatically and/or manually escaped from.


The use of headings in the work fully and accurately reflects the document hierarchy, allowing navigation by assistive technologies.


The structures in a PDF have been tagged to improve the navigation of the content.

Features for content control

The following values identify aspects of the content that users can control to improve access to the content. Do not confuse these control features with the accessibilityControl property, which defines input methods used to control the content.

Expected Values Description


Describes a resource that offers both audio and text, with information that allows them to be rendered simultaneously. The granularity of the synchronization is not specified. This term is not recommended when the only material that is synchronized is the document headings.


For content with timed interaction, this value indicates that the user has the ability to control the timing to meet their needs (e.g., pause and reset)


No digital rights management or other content restriction protocols have been applied to the resource.

Features for augmentation

Augmentation is the provision of intellectual content in a different access mode from its source.

Expected Values Description


Alternative text is provided for visual content (e.g., via the HTML alt attribute).


Audio descriptions are available (e.g., via an HTML5 track element with kind="descriptions").


The content is in braille format, or alternatives are available in braille. This value can be extended to identify the different types of braille (/ASCII, /unicode, /music, /math, /chemistry or /nemeth), and whether the braille is contracted or not (/grade1 and /grade2). Other extensions such as the code the braille conforms to can also be specified.


Indicates that synchronized captions are available for audio and video content.


Identifies that chemical information is encoded using the ChemML markup language.


Textual descriptions of math equations are included, whether in the alt attribute for image-based equations, using the alttext attribute for MathML equations, or by other means.

latex MathML

Identifies that mathematical equations and formulas are encoded using the designated markup language.


Descriptions are provided for image-based visual content and/or complex structures such as tables, mathematics, diagrams and charts.


Indicates that ruby annotations are provided in the content. Ruby annotations are used as pronunciation guides for the logographic characters for languages like Chinese or Japanese. It makes difficult Kanji or CJK ideographic characters more accessible. The absence of ruby/annotations/* implies that no CJK ideographic characters have ruby.


Synchronized sign language intepretation is available for audio and video content. The value may be extended by adding an ISO 639 sign language code. For example, /sgn-en-us for American Sign Language.


Tactile graphics are provided. For example, as described in the BANA Guidelines and Standards for Tactile Graphics.


The content is a tactile 3D object, or the model to generate one is included.


Indicates that a transcript of the audio content is available.


One or more of SSML, PLS lexicons and CSS3 Speech properties has been used to enhance text-to-speech playback quality.

accessibilityHazard in detail

schema.org's property definition of accessibilityHazard

accessibilityAPI in detail

schema.org's property definition of accessibilityAPI

accessibilityControl in detail

schema.org's property definition of accessibilityControl

accessMode in detail

schema.org's property definition of accessMode

The Access for All Digital Resource Description Specification Information Model from IMS Global defines an accessMode property that describes "an access mode through which the intellectual content of a described resource or adaptation is communicated". The allowed values for the property include textual, visual, auditory, tactile. The accessMode property of a single digital resource can have multiple values.

The main drawback of using accessMode in our context is that it does not describe to the primary mode of access. For instance, a text-based publication which happen to also contain a few images and one audio sample would have an accessMode property with values textual, visual, and auditory, with no indication of which mode is primary, or whether the entire content is accessible with a certain mode. This is where accessModeSufficient can further refine the combinations of accessModes that are needed to consume the content.

accessModeSufficient in detail

schema.org's property definition of accessModeSufficient

accessibilitySummary in detail

schema.org's property definition of accessibilitySummary

Example Markup

Example 1 (Book)

The following example shows how the accessibility metadata is used to enhance Bookshare records. A description of the process of adding this metadata, and a corpus of searchable books, can be found at the accessibility metadata website.

 1 <div itemscope="" itemtype="http://schema.org/Book">
 2    <meta itemprop="bookFormat" content="EBook/DAISY3"/>
 3    <meta itemprop="accessibilityFeature" content="largePrint"/>
 4    <meta itemprop="accessibilityFeature" content="highContrastDisplay"/>
 5    <meta itemprop="accessibilityFeature" content="displayTransformability/resizeText"/>
 6    <meta itemprop="accessibilityFeature" content="longDescription"/>
 7    <meta itemprop="accessibilityFeature" content="alternativeText"/>
 8    <meta itemprop="accessibilityFeature" content="readingOrder"/>
 9    <meta itemprop="accessibilityFeature" content="structuralNavigation"/>
10    <meta itemprop="accessibilityFeature" content="tableOfContents"/>
11    <meta itemprop="accessibilityControl" content="fullKeyboardControl"/>
12    <meta itemprop="accessibilityControl" content="fullMouseControl"/>
13    <meta itemprop="accessibilityHazard" content="noFlashingHazard"/>
14    <meta itemprop="accessibilityHazard" content="noMotionSimulationHazard"/>
15    <meta itemprop="accessibilityHazard" content="noSoundHazard"/>
16    <meta itemprop="accessibilityAPI" content="ARIA"/>
17    <dl>
18       <dt>Name:</dt>
19       <dd itemprop="name">Holt Physical Science</dd>
20       <dt>Brief Synopsis:</dt>
21       <dd itemprop="description">NIMAC-sourced textbook</dd>
22       <dt>Long Synopsis:</dt>
23       <dd>N/A</dd>
24       <dt>Book Quality:</dt>
25       <dd>Publisher Quality</dd>
26       <dt>Book Size:</dt>
27       <dd itemprop="numberOfPages">598 Pages</dd>
28       <dt>ISBN-13:</dt>
29       <dd itemprop="isbn">9780030426599</dd>
30       <dt>Publisher:</dt>
31       <dd itemprop="publisher" itemtype="http://schema.org/Organization" itemscope="">Holt, Rinehart and Winston</dd>
32       <dt>Date of Addition:</dt>
33       <dd>06/08/10</dd>
34       <dt>Copyright Date:</dt>
35       <dd itemprop="copyrightYear">2007</dd>
36       <dt>Copyrighted By:</dt>
37       <dd itemprop="copyrightHolder" itemtype="http://schema.org/Organization" itemscope="">Holt, Rinehart and Winston</dd>
38       <dt>Adult content:</dt>
39       <dd><meta itemprop="isFamilyFriendly" content="true"/>No</dd>
40       <dt>Language:</dt>
41       <dd><meta itemprop="inLanguage" content="en-US"/>English US</dd>
42       <dt>Essential Images:</dt>
43       <dd>861</dd>
44       <dt>Described Images:</dt>
45       <dd>910</dd>
46       <dt>Categories:</dt>
47       <dd><span itemprop="genre">Educational Materials</span></dd>
48       <dt>Grade Levels:</dt>
49       <dd>Sixth grade, Seventh grade, Eighth grade</dd>
50       <dt>Submitted By:</dt>
51       <dd>Bookshare Staff</dd>
52       <dt>NIMAC:</dt>
53       <dd>This book is currently only available to public K-12 schools and organizations in the United States for use with students with an IEP, because it was created from files supplied by the NIMAC under these restrictions. Learn more in the NIMAC Support Center.</dd>
54    </dl>
56    <div class="bookReviews" itemprop="aggregateRating" itemscope itemtype="http://schema.org/AggregateRating">
57       <h2>Reviews of Holt Physical Science (<span itemprop="reviewCount">0</span> reviews)</h2>
59       <div class="bookReviewScore">
60          <span><span itemprop="ratingValue>0</span> - No Rating Yet</span>
61       </div>
62    </div>
63 </div>

(The source record can be found at https://www.bookshare.org/browse/book/190639.)

Example 2 (Video)

This example shows how the accessibility metadata can be used to augment a record for a video.

 1 <dl itemtype="http://schema.org/VideoObject" itemscope="">
 2   <dt>Title:</dt>
 3   <dd itemprop="name">Arctic Climate Perspectives</dd>
 4   <dt>Description:</dt>
 5   <dd itemprop="description">This video, adapted from material provided by the ECHO partners,
 6     describes how global climate change is affecting Barrow, Alaska.</dd>
 7   <dt>Adaptation Type:</dt>
 8   <dd><span itemprop="accessibilityFeature">captions</span></dd>
 9   <dt>Access Mode:</dt>
10   <dd>auditory, visual</dd>
11   <dt>URL:</dt>
12   <dd><a itemprop="url" href="http://www.teachersdomain.org/asset/echo07_vid_climate">http://www.teachersdomain.org/asset/echo07_vid_climate</a>/</dd>
13   <dt>Has Adaptation:</dt>
14   <dd>http://www.teachersdomain.org/asset/echo07_vid_climate_dvs/</dd>
15   <dt>Subjects:</dt>
16   <dd><span itemprop="about">National K-12 Subject::Science::Earth and Space Science::Water Cycle, Weather,
17     and Climate::Structure and Composition of the Atmosphere, National K-12 Subject::Science::Earth and
18     Space Science::Water Cycle, Weather, and Climate::Climate</span></dd>
19   <dt>Education Level:</dt>
20   <dd>Grade 6, Grade 7, Grade 8, Grade 9</dd>
21   <dt>Audience:</dt>
22   <dd><span itemprop="intendedEndUserRole">Learner</span></dd>
23   <dt>Resource Type:</dt>
24   <dd><span itemprop="genre">Audio/Visual</span>, <span itemprop="genre">Movie/Animation</span></dd>
25   <dt>Language:</dt>
26   <dd><span itemprop="inLanguage">en-US</span></dd>
27   <dt>Publication Date:</dt>
28   <dd itemprop="datePublished">2007-02-12</dd>
29   <dt>Rights:</dt>
30   <dd>Download and Share, <a itemprop="useRightsUrl" href="http://www.teachersdomain.org/oerlicense/2/">http://www.teachersdomain.org/oerlicense/2/</a></dd>
31 </dl>

Issues Tracker and Open Issues

Issue Tracker, both open and closed

Discussion and Related Work