9. Media Accessibility

The edX documentation team is committed to providing resources that are accessible to everyone. The following information was originally written by Mark Sadecki, the edX accessibility specialist, for course teams who need to prepare accessible media. Its content is also useful for writers who are preparing instructional videos and technical documentation.

9.1. Introduction

Sometimes it can be helpful to start any discussion on media accessibility by dispelling common myths and talking about the challenges people with disabilities face when consuming media before talking about the solutions. Mark put together the following information about how people with disabilities consume media, what their challenges are, and how authors can provide solutions.

9.2. Blindness

People who are blind cannot access the visual information contained in videos. Some would conclude that the visual medium is inherently inaccessible to those who cannot see. However, audio and digital text are still very accessible. In accessibility we often talk about “alternative content.” With regard to media, audio and text can easily serve as alternative content for the blind. Good alternative content is equivalent content. Content is equivalent to other content when both fulfill the same function or purpose when presented to the user.

9.2.1. Things to Keep in Mind

Here are a few things to keep in mind when creating media for your courses.

  • Vocalize any print that appears in your video.

  • Explain visual events that are important to the context of the video. This will improve the quality of your material, ensuring that all students understand the significance of what they are observing.

  • Avoid using phrases like “over here we have…” or “this number…” that rely on a visual cue to comprehend.

9.2.2. How These Techniques Can Benefit a Broader Audience

Learners are increasingly consuming media while performing other tasks, such as driving, doing household chores, and so on, and they may not be able to focus on the video content at all. Try listening to only the audio track from your video. Is the information presented “equivalent”?


With regard to blindness, Mark feels that it is important to drive home the fact that if you do not vocalize unspoken visual events that are important to understanding the video, you will trigger a requirement to provide audio descriptions, which is both expensive and time consuming.

9.3. Low Vision

People with low vision can access some visual information. Depending on their visual ability, they might have specific issues such as difficulty discerning foreground information from background information, or discerning between colors. They may be unable to react quickly to transient information, and may have a narrow angle of view and so may not detect key information presented temporarily where they are not looking, or in text that is moving or scrolling.

A person with low vision is likely to use screen magnification software. This means that they will only be viewing a portion of the screen, and so must manage tracking media content.

Others with low vision may have difficulty reading when text is too small, has poor background contrast, or when decorative fonts or effects are used. Users with low vision often benefit from the same vocalization techniques used to provide access to those who are blind.

9.3.1. Things to Keep in Mind

  • Make sure important visual content remains on the screen long enough to be processed.

  • Consider contrast and lighting when choosing settings and adding visual content.

  • Use as much of the viewport as possible to present information.

  • Be consistent with the placement of important visual information.

9.3.2. How These Techniques Can Benefit a Broader Audience

Multimedia is increasingly being consumed on mobile devices that have a very small viewport. Many of the techniques mentioned above will benefit users who consume your content on a mobile device.

9.4. Deafness

People who are deaf generally cannot access the audio content of your media. As a result, an alternative format is required. On edX, this is provided through synchronized captions.

9.4.1. Things to Keep in Mind

When creating timed-text caption files, be sure to include descriptions of audible, non-speech content that is important to comprehending the video (such as [APPLAUSE], [BUZZER], [ASCENDING TONE]).

The text should “fulfill the same function or purpose” as the audio.

9.4.2. How These Techniques Can Benefit a Broader Audience

Captions are useful for those who do not speak the same language as the speaker in the video. Onscreen text is easier to comprehend than spoken words. Captions can also be translated into other languages very easily.

9.5. Hard of Hearing

People who are hard of hearing may be able to access some audio material, but might not be able to discern certain types of sound, and may miss any information presented as audio only if it contains frequencies they can’t hear, or is masked by background noise or distortion. They may miss audio which is too quiet, or of poor quality. People with cochlear implants may not have issues with audio volume levels, but comprehension may be challenging if the media experience is overwhelming. People who are deaf or hard of hearing may also read lips.

9.5.1. Things to Keep in Mind

  • Speak loudly and clearly.

  • Try to face the camera as much as possible when speaking onscreen.

  • Avoid background noise and/or music that competes with the primary audio.

9.6. WCAG 2 AA Requirements for Media

EdX is committed to satisfying the requirements defined in WCAG 2.0 Level AA. Excerpted below are the WCAG 2.0 guidelines that refer specifically to media. The goal of any training done at edX should be to ensure that course teams create content that satisfies these criteria.

9.6.1. Principle 1: Perceivable

Information and user interface components must be presentable to users in ways they can perceive. Guideline 1.1 Text Alternatives

Provide text alternatives for any non-text content so that it can be changed into other forms people need, such as large print, braille, speech, symbols or simpler language. 1.1.1 Non-text Content

All non-text content that is presented to the user has a text alternative that serves the equivalent purpose, except for the situations listed below. (Level A)

  • Time-Based Media: If non-text content is time-based media, then text alternatives at least provide descriptive identification of the non-text content. (Refer to Guideline 1.2 for additional requirements for media.)

  • Guideline 1.2 Time-based Media: Provide alternatives for time-based media. 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. 1.2.2 Captions (Prerecorded)

Captions are provided for all prerecorded audio content in synchronized media, except when the media is a media alternative for text and is clearly labeled as such. (Level A) 1.2.3 Audio Description or Media Alternative (Prerecorded)

An alternative for time-based media or audio description of the prerecorded video content is provided for synchronized media, except when the media is a media alternative for text and is clearly labeled as such. (Level A) 1.2.4 Captions (Live)

Captions are provided for all live audio content in synchronized media. (Level AA) 1.2.5 Audio Description (Prerecorded)

Audio description is provided for all prerecorded video content in synchronized media. (Level AA)

9.7. Audio Description

Most people are not familiar with audio descriptions. This video was made expressly to demonstrate both the need for, and the level of detail required for, quality audio description. It also happens to be a good example of quality captioning as well.

The Interviewer - Captions and Audio Descriptions