Note: The creation of this content was human-based, with the assistance on artificial intelligence.

Explanation of the success criteria

WCAG 1.2.1 Audio-only and Video-only (Prerecorded) is a Level A conformance level Success Criterion. For prerecorded audio-only or video-only content, providing an alternative (e.g., a transcript for audio-only, or an audio description/text alternative for video-only content) is required.

Audio-Only

Examples of audio-only content include:

  • Audio Tours
  • Audiobooks
  • Music Tracks
  • Phone-based Menus/IVR Systems
  • Podcasts
  • Voicemail Messages

For prerecorded audio-only content, a text transcript must be provided so users who are deaf or hard of hearing can access the same information.

Video-only

Examples of video-only content include:

  • Animated GIFs
  • Demonstration Videos (no audio)
  • Digital Signage
  • Instructional Animations (no audio)
  • Product Rotations/360 Views
  • Silent Movies
  • Silent Surveillance Footage
  • Time-lapse Videos

A transcript provides a text-based equivalent of video content, while an audio alternative can serve as an equivalent for visual information. This allows both vision-impaired and sighted users to access content simultaneously and supports those with cognitive, language, or learning disabilities through parallel presentation.

A text equivalent is not required when audio replaces video with no sound—for example, captions aren’t needed for audio descriptions of a silent film.

Testing via automated testing

Automated accessibility testing can detect media elements and verify the presence of basic alternatives, but it cannot assess their quality or meaning. It is fast, scanning code and markup quickly, and highly scalable, making it ideal for large-scale evaluations.

However, automated testing is limited to markup presence, not meaning or quality. It cannot evaluate the completeness or accuracy of alternatives and lacks context awareness. As a result, it has a high risk of false positives and negatives.

Testing via AI

AI-based accessibility testing can detect audio or video-based media using content analysis. It can also identify associated text or audio alternatives using content relationships. AI can performed these tasks quickly, with fast, scalable processing on media and text layers.

While AI can quickly handle identifying audio and video media, it can only check for basic semantic match in alternatives and struggles with nuance or intent. It can only detect syncing issues if aligned tracks are provided. It has limited understanding of context; content mismatches or missing data. And it may misclassify ambiguous or complex content.

Manual testing

In manual accessibility testing, a human tester confirms if content is audio-only or video-only, verifying whether a transcript or description is provided. They evaluate whether the alternative fully represents the original content and can judge the clarity, accuracy, and alignment of the alternative with source content. The human tester checks for alignment of timing or sync issues where needed. They also understand the purpose of the content and whether an alternative is appropriate. There are very few if any false positives or negatives.

The primary downsides is the scalability, as this testing is labor intensive, and that the testing is slower than more automated methods, as it requires a full content review.

Which approach is best?

No single approach guarantees appropriate alternatives for audio-only and video-only content. However, using the strengths of each approach in combination can have a positive effect.

Automated accessibility testing can be used for an initial scan for missing or broken alternatives. It can identify media elements and check for basic alternative presence, but not quality or meaning. AI-based accessibility testing helps with pattern recognition, content mapping, and can flag missing or low-quality alternatives, though human review is still essential for final evaluation. Both automated and AI-based accessibility testing can scale, to cover the breadth of an entire digital product. However, manual accessibioity testing is required to ensure the highest quality and most accurate assessment of alternatives for audio-only and video-only content.

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