Slide Deck Accessibility Checker
Check a Markdown slide deck: contrast, slide titles, alt text, reading order and text size.
How it works
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.
- 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.
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.
Sources
Part of Deckwright
-
Deckwright Slide deck studio
Write Markdown, get an accessible slide deck — charts, diagrams, PDF, HTML and PowerPoint.
Related tools
- Markdown to Slides (PDF and HTML) – Turn Markdown into a clean slide deck — PDF with embedded fonts and a single-file HTML presentation.
- Markdown to PowerPoint (PPTX) – Editable PowerPoint from Markdown: real titles, bullets, tables, speaker notes and alt text.
How to use the Slide Deck Accessibility Checker
Check a Markdown slide deck for missing slide titles, alternative text, contrast, reading order, vague link text, language and text size before you present or share it.
What it is for
Slides are often shared after the talk as PDF or PowerPoint, and that is where accessibility problems appear: slides without titles, pictures without descriptions, pale text on a pale background, links that say “here”. This checker looks at a Markdown deck as Deckwright lays it out and lists those problems with the slide number and the WCAG 2.2 success criterion.
It checks the colour pairs of the theme (WCAG contrast formula), slide titles and duplicate titles, alternative text for images, charts and diagrams, file names used as alt text, the reading order per slide, link text, the deck language, text that had to shrink or does not fit, empty slides and text-heavy slides. It cannot judge whether a description is accurate or whether the content is easy to understand.
Worked example
The default input is the six-slide lesson “How plants make food” in the Harbor theme. It passed: 0 errors, 0 warnings and 1 note — slide 4 has text at 10.5 pt, the mind map labels. The contrast table lists ten colour pairs; the weakest is “Subtitles on title slides” at 5.15:1 against the 4.5:1 that WCAG 1.4.3 asks for, body text reaches 13.17:1.
The broken example is a deck written in a hurry. It failed with 2 errors, 3 warnings and 1 note:
- Slides 2 and 4 have no title (WCAG 2.4.6).
- Slides 1 and 3 are both called “Results”.
- The image on slide 2 has the alt text “image.png”, which looks like a file name (WCAG 1.1.1).
- The link text “here” on slide 2 does not say where it goes (WCAG 2.4.4).
- The deck does not state its language (WCAG 3.1.1).
Running the quarterly review with Theme set to Midnight shows how a dark theme scores: body text 14.42:1, titles 10.71:1.
How to read the result
- Passed: true when there are no errors. Warnings still deserve a look.
- Findings: severity (error, warning or note), slide number, an explanation with a fix, and the WCAG criterion.
- Contrast: each colour pair, the measured ratio and the ratio needed (4.5:1 for text, 3:1 for large titles and graphics).
- Slides: the reading order — title, then the blocks in Markdown order — the smallest text in points, the word count and whether notes exist.
Tips and common mistakes
- Fix errors first: a missing slide title makes a deck hard to navigate with a screen reader.
- A chart without
alt:only gets a note, because the tool writes a summary from the data — your own sentence is still better. - Text below 10 pt is a warning, 10–12 pt a note; chart labels are often in that range.
- Add
lang:to the front matter even for English decks.
FAQ
Does a pass mean my deck is accessible?
No. It means the structural checks found nothing. Read your descriptions and check the content with real users.
Which WCAG version is used?
WCAG 2.2, level AA thresholds.
Can it check a PowerPoint file?
No, it checks Markdown. Decks made with Deckwright carry the same titles, alt text and order into PDF, HTML and PPTX.
Why are 10.5 pt diagram labels only a note?
They are readable on screens; in large rooms, bigger diagrams with fewer words work better.
Guide last updated:
For scripts and AI agents
- JSON API:
POST https://deckwrightdecka11ycheck.usefulweb.site/api/v1/calculate(same calculation as this page) - Interface description: OpenAPI 3.1 · AI guide: llms.txt
- MCP server (Streamable HTTP):
https://deckwrightdecka11ycheck.usefulweb.site/mcp· tool namedeckwright_deck_a11y_check
Example request
curl -s -X POST https://deckwrightdecka11ycheck.usefulweb.site/api/v1/calculate \
-H 'content-type: application/json' \
-d '{…see OpenAPI examples…}'