Accessible media

Deckset uses media descriptions in accessible PDF and HTML exports. Add alt(...) to the same modifier area used for layout and playback options:

![inline alt(Quarterly revenue increased by 18 percent)](revenue-chart.png)
![inline alt(A short product demonstration) autoplay](demo.mov)

Describe what the media communicates, not just its filename. Include visual details when they help someone understand the slide, and avoid repeating nearby text unless necessary.

Informative and decorative intent

Use informative when the media conveys information that must be available to assistive technology:

![informative alt(A map showing the three office locations)](offices.png)

This is especially useful for a meaningful full-slide or split background. An informative item should also have an alt(...) description.

Use decorative when the media adds no information and should be ignored by assistive technology:

![decorative](texture.png)

Do not add an alt(...) description to decorative media. If both intent modifiers appear, the last one wins.

Without an explicit intent:

• Media with alt(...) is informative.
• A background image without alt(...) is decorative.
• Foreground media without alt(...) is informative and can produce an export issue because it has no useful description.

These modifiers apply to images, SVG files, audio, video, YouTube embeds, and individual items in a media group. They also work in Obsidian media embeds.

Review warnings while you work

On macOS, open Presentation Options and turn on Show Accessibility Warnings. Deckset marks slides with missing or unrecognized media descriptions in the slide grid, Preview, and Floating Preview.

This option is off by default and is saved with the presentation. It only controls the warnings shown while you work. PDF and HTML export validation still runs whether the option is on or off.

Audio and video transcripts

An alt(...) description can name or summarize a recording, but it does not provide captions or a transcript. Add essential spoken information as visible text on the slide or in an accompanying transcript. Deckset does not currently have a Markdown command for attaching a caption track.

Describe Mermaid diagrams

Put a description command in the Mermaid fence metadata:

```mermaid, [.description: Checkout flow from cart to payment]
graph LR
  Cart --> Payment
```

desc is a shorter alias and quoted descriptions are supported:

```mermaid, [.desc: "Checkout: cart to payment"]
graph LR
  Cart --> Payment
```

The .description and .desc commands work with Mermaid, but not yet with Pikchr. Include essential diagram information as visible text, or use an image with a useful alt(...) description.

See Accessible PDF Export and HTML Export for export-specific validation and recovery behavior.