Understanding WCAG 2.0

Skip to Content (Press Enter)

This document is a draft, and is designed to show changes from a previous version. It is presently showing added text,changed text,deleted text,[start]/[end] markers,and Issue Numbers.

Hide All Edits   |   Toggle Deletions  |   Toggle Issue Numbers   |   Toggle [start]/[end] Markers   |   Show All Edits

Changes are displayed as follows:


Audio-only and Video-only (Prerecorded):
Understanding SC 1.2.1

1.2.1 Audio-only and Video-only (Prerecorded): For prerecorded audio-only and prerecorded video-only media, the following are true, except when the audio or video is a media alternative for text and is clearly labeled as such: (Level A)

  • Prerecorded Audio-only: An alternative for time-based media is provided that presents equivalent information for prerecorded audio-only content.

  • Prerecorded Video-only: Either an alternative for time-based media or an audio track is provided that presents equivalent information for prerecorded video-only content.

Intent of this Success Criterion

The intent of this Success Criterion is to make information conveyed by prerecorded audio-only and prerecorded video-only content available to all users. Alternatives for time-based media that are text based make information accessible because text can be rendered through any sensory modality (for example, visual, auditory or tactile) to match the needs of the user. In the future, text could also be translated into symbols, sign language or simpler forms of the language (future).

An example of pre-recorded video with no audio information or user interaction is a silent movie. The purpose of the transcript is to provide an equivalent to what is presented visually. For prerecorded video content, authors have the option to provide an audio track. The purpose of the audio alternative is to be an equivalent to the video. This makes it possible for users with and without vision impairment to review content simultaneously. The approach can also make it easier for those with cognitive, language and learning disabilities to understand the content because it would provide parallel presentation.

Note: A text equivalent is not required for audio that is provided as an equivalent for video with no audio information. For example, it is not required to caption video description that is provided as an alternative to a silent movie.

See also Understanding Success Criterion 1.2.9 Audio-only (Live)

Specific Benefits of Success Criterion 1.2.1:

  • This Success Criterion helps people who have difficulty perceiving visual content. Assistive technology can read text alternatives aloud, present them visually, or convert them to braille.

  • Alternatives for timed-based media that are text based may help some people who have difficulty understanding the meaning of prerecorded video content.

  • People who are deaf, are hard of hearing, or who are having trouble understanding audio information for any reason can read the text presentation. Research is ongoing regarding automatic translation of text into sign language.

  • People who are deaf-blind can read the text in braille.

  • Additionally, text supports the ability to search for non-text content and to repurpose content in a variety of ways.

Examples of Success Criterion 1.2.1

Related Resources

Resources are for information purposes only, no endorsement implied.

Techniques and Failures for Success Criterion 1.2.1 - Audio-only and Video-only (Prerecorded)

Each numbered item in this section represents a technique or combination of techniques that the WCAG Working Group deems sufficient for meeting this Success Criterion. The techniques listed only satisfy the Success Criterion if all of the WCAG 2.0 conformance requirements have been met.

Sufficient Techniques

Instructions: Select the situation below that matches your content. Each situation includes techniques or combinations of techniques that are known and documented to be sufficient for that situation.

Situation A: If the content is prerecorded audio-only:

  1. G158: Providing an alternative for time-based media for audio-only content

  2. Editorial Note: Unsure whether SL17 applies to this situation

Situation B: If the content is prerecorded video-only:

  1. G159: Providing an alternative for time-based media for video-only content

  2. G166: Providing audio that describes the important video content and describing it as such

Additional Techniques (Advisory) for 1.2.1

Although not required for conformance, the following additional techniques should be considered in order to make content more accessible. Not all techniques can be used or would be effective in all situations.

  • Providing a transcript of a live audio only presentation after the fact (future link)

  • Linking to textual information that provides comparable information (e.g., for a traffic Webcam, a municipality could provide a link to the text traffic report.) (future link)

Key Terms

alternative for time-based media

document including correctly sequenced text descriptions of time-based visual and auditory information and providing a means for achieving the outcomes of any time-based interaction

Note: A screenplay used to create the synchronized media content would meet this definition only if it was corrected to accurately represent the final synchronized media after editing.


a time-based presentation that contains only audio (no video and no interaction)

media alternative for text

media that presents no more information than is already presented in text (directly or via text alternatives)

Note: A media alternative for text is provided for those who benefit from alternate representations of text. Media alternatives for text may be audio-only, video-only (including sign-language video), or audio-video.


information that is not live


a time-based presentation that contains only video (no audio and no interaction)