# Reader support (/docs/reader-support)



This section is for **developers of reading applications**. An ADT — an Accessible Digital Textbook — is a publication enriched with narration, language variants, image descriptions, sign language, glossary data, and activities. This guide explains how a reader can make those capabilities available.

<SectionBanner slug="reader-support" />

<Callout type="idea" title="The integration model">
  An ADT export has two layers: a standard WebPub or EPUB that a conforming reader can open, and a compact ADT data layer that enriches the rendered content. Your reader can adopt one feature at a time.
</Callout>

## What works without ADT support [#what-works-without-adt-support]

| Capability                                    | EPUB                                                   | WebPub   |
| --------------------------------------------- | ------------------------------------------------------ | -------- |
| Open, navigation, TOC and page numbers        | Native                                                 | Native   |
| Read-aloud                                    | Native Media Overlays when present; otherwise ADT data | ADT data |
| Glossary                                      | Native EPUB glossary markup                            | ADT data |
| Language switching and Easy Read              | ADT data                                               | ADT data |
| Image descriptions, sign language, activities | ADT data                                               | ADT data |

**EPUB offers the most to an unmodified reader.** It can carry SMIL Media Overlays and EPUB-native glossary markup. WebPub keeps the feature data as sidecars, so the host reader owns the interface and behaviour.

## Start in this order [#start-in-this-order]

<Steps>
  <Step>
    ### Open and identify the package [#open-and-identify-the-package]

    Locate `assets/config.json`, resolve the package base path, and use the feature flags to decide which controls exist. See [Package and startup](/docs/reader-support/packages).
  </Step>

  <Step>
    ### Render the text layer [#render-the-text-layer]

    Apply the active language’s `texts.json` map to the elements on the rendered page. This establishes the join between the publication and the ADT data. See [Text and language](/docs/reader-support/text).
  </Step>

  <Step>
    ### Add the features your reader can support [#add-the-features-your-reader-can-support]

    Read-aloud, glossary, image descriptions, sign language, and activities are independent additions. Each guide includes the real exported data it consumes.
  </Step>

  <Step>
    ### Integrate with your reader shell [#integrate-with-your-reader-shell]

    Keep data loading, page injection, controls, cleanup, and validation in clear layers. See [Reader integration](/docs/reader-support/adapting).
  </Step>
</Steps>

## Find a feature [#find-a-feature]

<StageCards>
  <StageCard slug="reader-support/packages" href="reader-support/packages" title="Package and startup" description="Open an ADT, find its data layer, and discover available features." />

  <StageCard slug="reader-support/text" href="reader-support/text" title="Text and language" description="Language switching, Easy Read, content node ids, and localized text." />

  <StageCard slug="reader-support/read-aloud" href="reader-support/read-aloud" title="Read-aloud" description="Audio clips, word timing, and EPUB Media Overlays." />

  <StageCard slug="reader-support/glossary" href="reader-support/glossary" title="Glossary" description="Term maps in WebPub and native glossary markup in EPUB." />

  <StageCard slug="reader-support/images" href="reader-support/images" title="Image descriptions" description="Long descriptions and localized image variants." />

  <StageCard slug="reader-support/sign-language" href="reader-support/sign-language" title="Sign language" description="Per-page clips and a reader-controlled picture-in-picture surface." />

  <StageCard slug="reader-support/activities" href="reader-support/activities" title="Activities" description="Embedded activity runtime, reader chrome, and state limitations." />

  <StageCard slug="reader-support/adapting" href="reader-support/adapting" title="Reader integration" description="Architecture, layout fixes, cleanup, and an integration checklist." />
</StageCards>