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hAudio 0.7


hAudio is a simple, open, distributed format, suitable for embedding information about audio recordings in (X)HTML, Atom, RSS, and arbitrary XML. hAudio is one of several microformats open standards.

hAudio Microformat Draft Specification

Manu Sporny, Bitmunk - Digital Bazaar, Inc.
Manu Sporny, Bitmunk - Digital Bazaar, Inc.
Martin McEvoy
Alexandre Van De Sande Releases all his contribution as public domain(see user page)
Michael Johnson
Dave Longley
Brian Suda
Ben Wiley Sittler
Scott Reynen
Frances Berriman
James Craig
David Janes
Andy Mabbett
Danny Ayers
Rudy Desjardins
Edward O'Connor
Ryan King
Chris Griego
Brad Hafichuk
Tantek Çelik
Colin Barrett
Joe Andrieu
Michael Smethurst
Chris Newell
Julian Stahnke
Justin Maxwell
Paul Wilkins

Microformats #Copyright and #Patents statements apply.



It is difficult for a browser to extract semantic information about an audio recording described on a web page. Metadata such as speaker, musician, publisher, label, title of the work, release date, acquisition link, related image artwork and tags provide relevant context for the audio recording.

Having such information marked up can provide a number of benefits to the viewer. If a web browser understands that a particular web page contains a song performed by an artist, it can produce richer interactions. For example, specific searches may be performed for artists and songs via general search services such as Google and Wikipedia. Specific search services may also be queried such as MusicBrainz, The Internet Archive, FreeDB, or Bitmunk. Additionally, classification by crawlers can become more accurate. If there are 20 tracks found on a page done by the same artist, and that content consumes a significant portion of the page, it can be assumed that the page is not only about music, but also about a particular artist.

In order to enable and encourage the sharing, distribution, syndication, and aggregation of audio content, the authors propose the hAudio microformat, an open standard for distributed audio metadata. The authors have researched both numerous audio-info-examples in the wild and earlier attempts at audio-info-formats, and have designed hAudio around a simple minimal schema for audio content. Feedback is encouraged on the hAudio feedback page.

Inspiration and Acknowledgments

Many thanks to the various individuals that did research and proposed ideas and discussion related to media info and audio info in general. Among the many participants are RodBegbie, Dean Hudson, Tantek Çelik, Mary Hodder, Joshua Kinberg, ChrisMessina, and Lisa Rein.


Audio content consistently share several common fields. Where possible hAudio has been based on this minimal common subset.

Out of scope

Fields that are type-specific have been omitted from hAudio. It is important that hAudio be kept simple and minimal from the start. Additional features can be added as deemed necessary by practical implementation experience.

The concept of a universal audio identifier, that is, how to identify the same audio album, song, speech, or podcast across different music and audio sites, though something very useful to have, is outside the scope of this format.

Semantic XHTML Design Principles

Note: the Semantic XHTML Design Principles were written primarily within the context of developing hCard and hCalendar, thus it may be easier to understand these principles in the context of the hCard design methodology (i.e. read that first). Tantek

XHTML is built on XML, and thus XHTML based formats can be used not only for convenient display presentation, but also for general purpose data exchange. In many ways, XHTML based formats exemplify the best of both HTML and XML worlds. However, when building XHTML based formats, it helps to have a guiding set of principles.

  1. Reuse the schema (names, objects, properties, values, types, hierarchies, constraints) as much as possible from pre-existing, established, well-supported standards by reference. Avoid restating constraints expressed in the source standard. Informative mentions are ok.
    1. For types with multiple components, use nested elements with class names equivalent to the names of the components.
    2. Plural components are made singular, and thus multiple nested elements are used to represent multiple text values that are comma-delimited.
  2. Use the most accurately precise semantic XHTML building block for each object etc.
  3. Otherwise use a generic structural element (e.g. <span> or <div>), or the appropriate contextual element (e.g. an <li> inside a <ul> or <ol>).
  4. Use class names based on names from the original schema, unless the semantic XHTML building block precisely represents that part of the original schema. If names in the source schema are case-insensitive, then use an all lowercase equivalent. Components names implicit in prose (rather than explicit in the defined schema) should also use lowercase equivalents for ease of use. Spaces in component names become dash '-' characters.
  5. Finally, if the format of the data according to the original schema is too long and/or not human-friendly, use <abbr> instead of a generic structural element, and place the literal data into the 'title' attribute (where abbr expansions go), and the more brief and human readable equivalent into the element itself. Further informative explanation of this use of <abbr>: Human vs. ISO8601 dates problem solved


In General

The hAudio format is based on a set of fields common to numerous audio content sites and formats in use today on the web. Where possible field names have been chosen based on those defined by the related hCard standards.


The hAudio schema consists of the following:

Field details

The fields of the hAudio schema represent the following:


An hAudio is used to identify and describe metadata associated with an audio recording.

Formatted Name

The title of a single audio recording is a short textual description used to identify the work among interested parties. This can be the title of a speech, song title, or short description regarding a sound effect.


The title of a collection of audio recordings that are represented as a CD, album or LP. The text should be a short textual description used to identify the work among interested parties. This can be the title of a CD, album title, or the name of a collection of audio recordings.


A container for another hAudio item, which MUST be considered a part of the parent audio recording. An example of an item that is part of an hAudio would be a track in an audio album, a aria in an Opera, or a section of a podcast.


The position is used to describe the position of the hAudio item in a list. Examples of hAudio lists can include album track listings, music top 10 lists, playlists, and podcast chapters.


A Contributor is any entity that takes part in the creation and distribution of an audio recording. Examples include: artist, publisher, guitarist, vocalist, violinist, lead singer, backup singer, bassist, drummer, manager, and roadie.


The published date specifies the date that the audio recording was made available to the public. Examples include: The airing date of a radio broadcast, the day a speech was given, or the day a music album was made available for sale.


A Sample URL specifies from where an excerpt of the audio recording may be retrieved.

Full Download (Enclosure)

An Full Download URL specifies from where the full version of an audio recording may be retrieved. The URL MUST point to a direct link to a file.

Purchase (Payment)

An Purchase URL specifies from where the full version of an audio recording may be purchased. The URL MUST point to a page that contains a purchase process.


A photo specifies an image that should be used to summarize the audio recording. Examples include: the image of a speaker, an audio album cover image, or a picture from a concert.


The Category specifies the genre or style used to classify the audio recording. Examples include: blues, rock, motivational, spoken word, or sound effect.


The Duration specifies the length in time of the audio recording. Examples include: 104 seconds, 3:23, and 4 minutes.


The Price specifies the amount of currency that must be exchanged for acquisition of a full specimen of the audio recording. Examples include: One Dollar, $2, and £4.


An explanation of the contents of the hAudio item. This could explain the significance of a speech, the full-text description of a sound effect, or the meaning of a song or album.

More Semantic Equivalents

For some properties there is a more semantic equivalent, and therefore they get special treatment, e.g.:


Human vs. Machine Readable

If an <abbr> element is used for a property, then its 'title' attribute is used for the value of the property, instead of the contents of the element, which can then be used to provide a user-friendly alternate presentation of the value.

Similarly, if an <img /> element is used for one or more properties, it MUST be treated as follows:

  1. For the "photo" property and any other property that takes a URL as its value, the src="..." attribute provides the property value.
  2. For other properties, the <img /> element's 'alt' attribute is the value of the property.


This section is informative.

XMDP Profile

<dl class="profile">
  <a rel="help" href="http://www.w3.org/TR/html401/struct/global.html#adef-class">
   HTML4 definition of the 'class' attribute.</a>
  This meta data profile defines some 'class' attribute values (class names) 
  and their meanings as suggested by a 
  <a href="http://www.w3.org/TR/WD-htmllink-970328#profile">
   draft of "Hypertext Links in HTML"</a>.
    Used to identify and describe metadata associated with an individual audio recording.
    A short textual description used to identify an audio recording among interested parties.
    A short textual description used to identify an audio recording that is an album among 
    interested parties.
    An entity that takes part in the creation and distribution of an audio recording.
    The date that the audio recording was made available to the public.
    A verbose description of the audio recording.
    An image that should be used to summarize the audio recording.
    The genre or style used to classify the audio recording.
    The length of the audio recording.
    The amount of currency that must be exchanged for acquisition of a full specimen of the audio recording.


Here are a few examples of audio content from current web sites, and how they could be easily enhanced to support the hAudio audio metadata microformat.

Want to write valid hAudio? Use the hAudio creator (not implemented yet) to write about audio content and publish it on your blog.

Simple Song Example


Start Wearing Purple by Gogol Bordello

Microformatted XHTML:

<div class="haudio">
   <span class="fn">Start Wearing Purple</span> by 
   <span class="contributor">Gogol Bordello</span>

Speech Example


I Have a Dream, a speech by Martin Luther King Jr.

Microformatted XHTML:

<div class="haudio">	 
   <span class="fn">I Have a Dream</span>, a 	 
   <span class="category">speech</span> by 	 
   <span class="contributor">Martin Luther King, Jr.</span>

Song and Album Example


Start Wearing Purple by Gogol Bordello found on Underdog World Strike

Microformatted XHTML:

<div class="haudio">
   <span class="fn">Start Wearing Purple</span> by 
   <div class="contributor">
      <div class="vcard">
         <span class="org fn">Gogol Bordello</span>
   found on
   <span class="album">Underdog World Strike</span>

Complete Album Example

An example that uses every element of hAudio:

[Image] Live Phish, Volume 15 by Phish
Released: October 31, 2002
Acquire: Sample, Live Recording, Buy High Quality Track
Category: Live
Duration: 145 minutes, 27 seconds
Price: $14.99

1. Sanity (5:48)
2. Highway To Hell (3:39)

Here is the hAudio Microformat markup:

<div class="haudio">
   <img class="photo" src="images/live_phish_vol_15.jpg"/>
   <span class="album">Live Phish, Volume 15</span>
   <span class="contributor">
      <span class="vcard">
         <span class="fn org">Phish</span>
   Released on:
   <abbr class="published" title="20023110">October 31, 2002<abbr>
   <a rel="sample" href="/samples/live_phish_vol_15_sample.mp3">Sample</a>, 
   <a rel="enclosure" href="/live/phish_live_phish_vol_15.mp3">Live Recording</a>,
   <a rel="payment" href="/buy/phish_live_phish_vol_15">Buy High Quality Track</a>
   Category: <span class="category">live</span>
   Duration: <abbr class="duration" title="PT145M27S">145 minutes, 27 seconds</abbr>
   Price: <div class="price"><abbr class="currency" title="USD 14.99">$14.99</span></div>
   <div class="item">
      <span class="position">1</span>.
      <span class="fn">Sanity</span>
      (<abbr class="duration" title="PT5M48S">5:48</abbr>)
    <div class="item">
     <span class="position">2</span>.
     <span class="fn">Highway To Hell</span> 
     (<abbr class="duration" title="PT3M39S">3:39</abbr>)

Podcast with Multiple Parts

DigitalPlanet Podcast: 29 Oct 07

Forensic computing: is it really possible to delete data from your machine? Grand plans for getting broadband into Africa, checking out the sky at night via the internet and answering your emails to the programme.

Download MP3

<div class="haudio">
   <span class="fn">DigitalPlanet Podcast</span>
   <abbr class="published" title="20071029">29 Oct 07</abbr>
   <div class="item">
      <span class="fn">Forensic computing: is it really possible to delete data from your machine?</span>
   <div class="item">
      <span class="fn">Grand plans for getting broadband into Africa</span>
   <div class="item">
      <span class="fn">checking out the sky at night via the internet</span>
   <div class="item">
      <span class="fn">answering your emails</span>
   to the programme.
   <a rel="enclosure" href="/download/episode/DigitalPlanet-2007-10-29">Download MP3</a>


La Bohème is an opera in four acts by Giacomo Puccini to an Italian libretto by Luigi Illica and Giuseppe Giacosais. I saw it performed last week and found Act III to be pretty interesting, especially the "Sa dirmi, scusi" and "O buon Marcello, aiuto!" arias.

<div class="haudio" lang="en">
   <span class="fn" lang="it">La Bohème</span> 
   is an 
   <span class="category">opera</span> 
   in four acts by 
   <span class="contributor" lang="it">Giacomo Puccini</span>
   to an 
   <span class="category">Italian liberetto</span>
   <span class="contributor" lang="it">Luigi Illica</span>
   <span class="contributor" lang="it">Giuseppe Giacosais</span>.
   I saw it performed last week and found
   <div class="item">
      <span class="fn">Act III</span>
       to be pretty interesting, especially the
      <div class="item">
         "<span class="fn" lang="it">Sa dirmi, scusi</span>"
      <div class="item">
         "<span class="fn" lang="it">O buon Marcello, aiuto!</span>"

Examples in the wild

This section is informative.


This section is informative.

See hAudio Implementations.


Normative References

Informative References

Similar Work


This document and specification was placed into the public domain on July 25th, 2007 by the authors. There are no usage, distribution, re-printing, or any other restrictions of any kind with regards to the text or content of this specification.


The authors of this Microformat have not and will not apply for patents covering any invention covering this Microformat in part or as a whole. There are no claims to any patent in this document. Each author is required to report any known patent issues immediately under this section.

This document and specification is distributed under a royalty free patent policy, e.g. per the W3C Patent Policy (http://www.w3.org/Consortium/Patent-Policy-20040205/), and IETF RFC3667 (http://www.ietf.org/rfc/rfc3667.txt) & RFC3668 (http://www.ietf.org/rfc/rfc3668.txt).

Public Domain Release

The authors and editors of this page due hereby relinquish their copyright on the document and release the text of this page into the public domain.

Work in progress

This specification is a work in progress. As additional aspects are discussed, understood, and written, they will be added.

Further Reading

Mailing List Discussion

Specification Development Statistics

Related Pages

haudio was last modified: Wednesday, December 31st, 1969