About assistive technology
Audio descriptions, captions, alt text, and tagged PDFs are all outputs Content Studio produces, but none of them exist for their own sake — each one exists because a specific category of assistive technology, used by real people, depends on it. Understanding those tools makes it easier to judge what “good” output actually looks like, beyond just “technically present.”
Screen readers
Section titled “Screen readers”A screen reader converts what’s on screen into synthesized speech, or sends it to a refreshable braille display, and it’s the primary way blind and many low-vision people read a PDF, a web page, or an app. Critically, a screen reader has no access to how something looks — it can only work with structure: reading order, headings, list and table markup, and alt text on anything visual. A PDF that looks perfectly normal to a sighted reader can be silent or scrambled to a screen reader if that structure isn’t there, which is exactly the gap PDF accessibility remediation closes, and exactly why an image needs alt text even though nothing about its visual appearance changes.
Audio description
Section titled “Audio description”Audio description solves a narrower, different problem: video. A screen reader can read out what a caption says, but it has no way to describe what’s happening visually between lines of dialogue — a scene change, a facial expression, on-screen text, an action with no dialogue attached. Audio description fills exactly that gap, narrated into the video’s own natural pauses. It serves blind and low-vision viewers specifically, and it’s a separate track from captions — see About audio descriptions and captions for how the two relate.
Magnification, without a screen reader
Section titled “Magnification, without a screen reader”Not every low-vision person uses a screen reader — many rely on screen magnification, larger text, or higher contrast instead, without ever having anything read aloud. That group benefits from a different property of accessible content: real, selectable text rather than a flattened image of text. A PDF with real tagged text can be zoomed, reflowed, and have its contrast adjusted by the reader’s own software; a scanned image of a page can’t be any of those things, no matter how the file is presented.
Keyboard-only navigation and switch access
Section titled “Keyboard-only navigation and switch access”A meaningful number of people can’t use a mouse or touchscreen reliably — because of a motor disability, a temporary injury, or a tremor — and instead navigate entirely by keyboard, or with a switch device that steps through a page’s focusable elements one at a time. What both need is the same thing a screen reader needs: a sane, predictable order to move through. A document with a logical reading order is, not coincidentally, also one that’s sanely keyboard-navigable — the two properties come from the same underlying structure. (If you want to navigate Content Studio’s own editors this way, see Editor keyboard shortcuts.)
Captions
Section titled “Captions”Captions serve a different audience again: Deaf and hard-of-hearing viewers, and anyone watching without audio. They’re a text representation of dialogue and meaningful sound, not a narration of visuals — which is why a video needs both captions and audio description to be genuinely accessible to everyone, not one standing in for the other.
The throughline
Section titled “The throughline”Every one of these tools is a consumer of structure, not of appearance. That’s why Content Studio’s PDF tool is built around never changing how a document looks and only ever adding or correcting the structure underneath it, why alt text and audio description exist as outputs separate from the visual content itself, and why captions and audio description are kept as two distinct tracks rather than folded into one general “accessibility mode.” Good accessible output isn’t a visual style — it’s the invisible structure that makes all of these different tools work.