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WCAG: Web Content Accessibility Guidelines

The World Wide Web Consortium’s Web Content Accessibility Guidelines (WAI) are the leading international, nonpartisan standard for accessibility on the Web. Version 1.0 of WCAG, published in 1999, is still in effect, while Version 2.0 is under development.

WCAG 1.0

Multimedia are considered “Web content” and must be made accessible under WCAG 1.0. Checkpoint 1.4 states: “For any time-based multimedia presentation (e.g., a movie or animation), synchronize equivalent alternatives (e.g., captions or auditory descriptions of the visual track) with the presentation.” That’s a Priority 1 requirement; all sites claiming to meet the Web Content Accessibility Guidelines must meet the requirement if they provide multimedia.

(Priority 1 is the base level of accessibility, with Priority 2 and 3 as higher levels. You can’t meet the higher levels without meeting the immediately-lower level. Hence all sites with multimedia that claim to conform to WCAG 1.0 must provide captioned multimedia. Exceptions – as with silent videoclips – could be imagined, but are rare.)

Techniques to meet Checkpoint 1.4 include the following:

Auditory presentations must be accompanied by text transcripts, textual equivalents of auditory events. When these transcripts are presented synchronously with a video presentation they are called captions and are used by people who cannot hear the audio track of the video material.

WCAG 2.0

The long-anticipated update to the Web Content Accessibility Guidelines, namely version 2.0, had not been completed by the end of the TILE project. One draft that was current at the end of the project accurately represents the trend of WCAG 2.0 regarding captioning:

Guideline 1.2. Provide synchronized media equivalents for time-dependent presentations.

Level 1 Success Criteria for Guideline 1.2

  1. [...] Captions are provided for all significant dialogue and sounds in time-dependent material. [I]
  2. Descriptions and captions are synchronized with the events they represent. [I]
  3. If the Web content is real-time video with audio, real-time captions are provided. [I]
  4. If a presentation that contains only audio or only video requires users to respond interactively at specific times during the presentation, then a synchronized equivalent presentation (audio, visual or text) is provided. [I]

Exception: If content that is rebroadcast from another medium or resource meets accessibility requirements for that medium, then the rebroadcast satisfies this checkpoint if it complies with other applicable sections of WCAG 2.0

Level 2 Success Criteria for Guideline 1.2

  1. Synchronized captions are provided for all real-time broadcasts.

Strengths and weaknesses of WCAG 2.0

Both WCAG versions have the indisputable strength of requiring that multimedia be accessible. The exact methods that authors may use, though, are a weakness. WCAG 1.0 defines captions as a certain kind of transcript, but states that a transcript is all that’s required. Authors can meet Checkpoint 1.4 by simply providing a text or HTML document (or any kind of document) that transcribes whatever multimedia they provide. Synchronized transcripts – that is, captions – are not actually required.

In WCAG 2.0, the loophole to provide transcripts is removed, though the final 2.0 Guidelines may authorize providing nothing but a separate transcript under limited circumstances (e.g., video of very short duration, as yet undefined).

WCAG 2.0’s clause stating that multimedia that meets some other requirements automatically meets WCAG 2.0 is open to abuse. A broadcaster with a requirement to caption less than 100% of its programming can simply select uncaptioned programming and provide that online. (After all, that programming meets the requirement that only some of the broadcaster’s programming be captioned.)


Proposed captioning requirements

The WCAG Working Group held a meeting in Toronto in September 2003 at which some suggestions were made concerning WCAG 2.0’s captioning requirements. What follows is an update of those recommendations.


  1. It’s unrealistic to expect authors to caption all their videoclips right away.
    1. Expertise is an issue. With no known training programs, it’s also hard to develop.
    2. Player complications are significant, and if the author provides video in multiple formats, then multiple incompatible caption formats will also be required.
    3. Captioning itself is difficult and captioning software makes things harder.
    4. Sending video out of house for captioning costs hundreds or thousands of dollars per program hour. For many small and medium-size Web publishers, that constitutes undue hardship right there.
    5. In some languages and countries, there is no tradition or practice of captioning at all, even on television.


  1. Transcription is not the way to make video accessible. The correct accessibility method is captioning.
  2. A transcript is an artifact separate from the original, just as a talking book or large-print or Braille edition is separate from a printed book. But audiovisual media can and must carry their accessibility features with them.
  3. If an online video segment is provided with captions, a transcript can be added and offered later. A transcript must never be the sole method of accessibility for deaf and hard-of-hearing viewers. At best it can be supplemental.
  4. A “combined” caption transcript plus audio-description script have been attempted only rarely – for only a tiny handful of known projects (including DigNubia). These combined transcripts can be manually assembled, but there is no automated method to combine those two sources – due, among other reasons, to a lack of interchange formats and the difficulty of autoconverting into valid, semantic XHTML.

Reuse of existing captions and descriptions

  1. Authors should be required to reuse any captions or descriptions that were created for the original program.
  2. That means all TV programming captioned or described for television must carry its accessibility over to the Web.
  3. It’s technically straightforward, inexpensive, and almost immediately achievable, even for audio description.
  4. It’s already being done now.

Standards analogous to WCAG

The Web Content Accessibility Guidelines are not the only Web-accessibility standard, but all the others currently in place were derived from or are analogous to WCAG.

Section 508

Section 508 of the Rehabilitation Act of 1973 applies to U.S. federal government departments (with few exceptions) and a small number of federally-funded agencies and organizations. §1194.22 states:

Equivalent alternatives for any multimedia presentation shall be synchronized with the presentation.... Captioning for the audio portion and audio description of visual information of multimedia presentations are considered equivalent alternatives.

Note that the 508 requirements do not permit the use of a separate transcript to comply:

This provision requires that when an audio portion of a multimedia production is captioned... the captioning must be synchronized with the audio. Synchronized captioning would be required so someone reading the captions could also watch the speaker and associate relevant body language with the speech.

(There is, nonetheless, an ambiguity in the 508 specification, since it says that these multimedia requirements are “consistent” with Checkpoint 1.4 of WCAG 1.0, which permits transcripts. Still, that note could be viewed as incidental and purely informative.)

Audio-only files don’t have to be captioned “because it is not multimedia. However, since audio is a non-text element, a text equivalent, such as a transcript, must be available.”


The German BITV regulations require:

Für jede zeitgesteuerte Multimedia-Präsentation (insbesondere Film oder Animation) sind äquivalente Alternativen (z.B. Untertitel oder Audiobeschreibungen der Videospur) mit der Präsentation zu synchronisieren.

(English: “For each time-based multimedia presentation [in particular, film or animation], equivalent alternatives [e.g. subtitles or audio descriptions of the video source] are to be synchronized with the presentation.”)

EU and Italy

The European Union and Italy have adopted WAI standards directly.