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1 October 2021

The World Wide Web Consortium (W3C) Web Accessibility Initiative (WAI) has recently published the First Public Working Draft of the Note on Synchronization Accessibility User Requirements (SAUR).

Synchronization of multimedia content, especially audio and video, is essential for accessible web-based communication and cooperation. To be understandable, media needs to be synchronized to very specific limits when providing accessibility options such as captions. Synchronization Accessibility User Requirements (SAUR) addresses synchronization of accessibility-related components of multimedia, including:

  • captions
  • sign language interpretation
  • descriptions

It identifies accessibility user needs and the associated requirements for multimedia synchronization. The requirements apply to multimedia content in general, as well as to real-time communication applications and media in immersive environments.

In preparing the document, The Research Questions Task Force (RQTF) of the Accessible Platform Architectures (APA) Working Group looks at identifying tolerances and seeking to give informed answer such as

  • “how much delay can occur between any related audio and video tracks?” or
  • “what are acceptable tolerances between speech and captions before comprehension is adversely affected?”

These findings are then summarized in the First Public Working Draft of Synchronization Accessibility User Requirements (SAUR).

This Note is intended to inform future development of media technologies, W3C specifications, and accessibility guidelines. It may also be applied to multimedia content and applications to enhance accessibility.

Dr Scott Hollier, CEO of CFA Australia, was an editor for the document and noted at its release, “It’s great to see this important work reaching public consultation. Accessibility only works if the features such as captions are synroncised correctly with the media it supports, so it’s great that guidance on this can be published to support media creators in this area.”

To read the first public working draft of the document, visit the W3C page.

To learn more about the document and information, visit the W3C blog post.

For in-progress updates to the document, see the Editor’s Draft on the W3C page.

Reviews and comments on the First Public Working Draft are encouraged.

To comment, open a new issue in the APA GitHub repository.

Add the label “SAUR” and create separate GitHub issues for each topic, rather than commenting on multiple topics in a single issue.

If GitHub is not feasible, send comments in e-mail to

Comment by: 5 November 2021