# Slide Deck Accessibility Checker

> Check a Markdown slide deck: contrast, slide titles, alt text, reading order and text size. Lays out a Markdown deck exactly like the Deckwright exports and checks it: WCAG 2.2 contrast of every colour pair of the theme, a unique title on every slide, alternative text for images, charts and diagrams, the reading order of each slide, link texts, the deck language, text that had to shrink or does not fit, small chart and diagram labels, empty and very dense slides. Every finding names the slide and the WCAG success criterion.

Part of usefulweb.site (https://usefulweb.site/). Part of [Deckwright](https://deckwright.usefulweb.site/) (ownerApp: deckwright). Results are deterministic calculations from the inputs and the listed assumptions; the API returns exactly what the web page shows.

## Use it
- Human interface: https://deckwrightdecka11ycheck.usefulweb.site/ (interactive tool at https://deckwrightdecka11ycheck.usefulweb.site/tool)
- JSON API: POST https://deckwrightdecka11ycheck.usefulweb.site/api/v1/calculate with a JSON object of inputs (schema: https://deckwrightdecka11ycheck.usefulweb.site/api/v1/tool)
- OpenAPI: https://deckwrightdecka11ycheck.usefulweb.site/openapi.json
- MCP (Streamable HTTP): https://deckwrightdecka11ycheck.usefulweb.site/mcp - tool `deckwright_deck_a11y_check`

## Inputs
- markdown (textarea): Deck in Markdown - Slides are separated by a line ---; without separators every # or ## heading starts a slide.
- theme (select): Theme
- lang (text): Deck language (BCP 47, e.g. en, de, ar) - Leave empty to use “lang:” from the front matter (English if not set).

## Method
- Contrast: WCAG 2.2 relative luminance of the sRGB colours and (L1 + 0.05) / (L2 + 0.05) for every pair the theme draws; body text, links, code and subtitles need 4.5:1, titles (30 pt and larger) and graphical marks 3:1 (SC 1.4.3, 1.4.11).
- Structure: every slide needs a title and titles should be unique (SC 2.4.6; screen readers list PowerPoint and PDF slides by title); images need alternative text that is not a file name (SC 1.1.1); charts and diagrams without their own alt text are reported as using their generated description.
- Reading order (SC 1.3.2): the exports keep the Markdown order on every slide (title, then text and visuals as written); the report lists it per slide. Link texts such as “here” or “click here” are flagged (SC 2.4.4), a missing deck language too (SC 3.1.1).
- Layout checks run on the real layout: text that had to shrink, text that does not fit even at 14 pt, chart or diagram labels below 10 pt (warning) or 12 pt (note), slides without content and slides with more than 90 words.

## Limits
- An automatic check finds structural problems; it cannot judge whether alternative text is accurate or whether the slides make sense. Ask a screen reader user to try important decks.