Show HN: Whitedeck – Black on White Keynote Like Slides Claude Skill

The content is the design. whitedeck turns markdown into slides in Apple Keynote's plain White theme: HTML, PDF, editable PPTX and native .key, with Apple's own layout geometry. Built for Claude Code and other AI agents, so their decks stop looking like AI decks.

npm install -g https://github.com/franzenzenhofer/whitedeck/archive/refs/heads/main.tar.gz
whitedeck init my-deck.md
whitedeck build my-deck.md -f all

Ask an AI agent for slides and it decorates: gradients, glow, emoji for icons, a card around every bullet, a headline that names a topic instead of making a point. It looks busy and says little.

whitedeck takes all of that off the table. White canvas, one typeface, one claim per headline, the evidence on the slide and its source underneath. There is nothing to fiddle with, so the only thing left to improve is the argument. Pretty slides are a sign of the wrong priorities.

Same four facts on both slides. One wants to be admired, the other gets read.

Under the plain look sits provably exact geometry: every placeholder position, size, font and point size is extracted from Apple's own Keynote export into one source of truth (src/theme/white.json) and asserted by integration tests in every output format.

Every image below is a page of docs/showcase/showcase.md, rendered by whitedeck build showcase.md -f pdf.

| title | title-bullets | | compare | photo-horizontal | | title-center | title-bullets-photo | | bullets | quote |

whitedeck runs on macOS, Linux and Windows with Node.js 20 or newer. No Keynote and no PowerPoint needed for anything but .key.

npm install -g https://github.com/franzenzenhofer/whitedeck/archive/refs/heads/main.tar.gz
whitedeck init my-deck.md
whitedeck build my-deck.md -f all

The commands are the same in Terminal, bash, PowerShell and cmd.

-f all builds every format this machine can build: html + pdf + pptx (+ key on a Mac with Keynote). Every format it leaves out gets one line on stderr, and the exit code stays 0:

skipped key: Keynote is macOS-only (this machine runs Linux). Fix: use -f pptx, which opens in PowerPoint, Keynote, LibreOffice Impress and Google Slides

A format you name explicitly must be buildable: -f key on Linux, or -f pdf without a browser, stops before anything is written, exit 1, one line with the reason and the fix.

Which browser prints the PDF: CHROME_PATH if set (a wrong path is an error, not a fallback), else the first one found among installed Chrome, Chromium and Edge (Windows: the Program Files and LocalAppData install folders; Linux: google-chrome, chromium, microsoft-edge on PATH, /opt, /snap; macOS: /Applications and ~/Applications), else a browser downloaded by npx playwright install chromium or npx @puppeteer/browsers install chrome. No browser at all: install Chrome or Edge, or run npx playwright install chromium.

CI builds the examples with -f all on ubuntu, windows and macos runners on every push.

Slides are separated by ---. A comment picks one of the 12 Keynote White layouts; without it, whitedeck infers a sensible one.

---
title: My Deck
author: Me
---

<!-- _class: title -->
## Subtitle

---

<!-- _class: title-bullets -->
- First point
- Second point
  - Nested detail

---

<!-- _class: quote -->
> "Simplicity is the ultimate sophistication."
> -- Leonardo da Vinci

---

<!-- _class: photo-horizontal -->
## A caption
![](ocean.png)

Source: [GSC Performance](https://search.google.com/search-console)

---

<!-- _class: compare -->
- **Before**
- LCP 4.1s
- **After**
- LCP 1.3s

Links [text](url) render blue and underlined in every format (real hyperlinks in PPTX). A final Source: [Name](url) line becomes a small source note at the bottom of the slide. Titles that would overflow their box auto-shrink, exactly like Keynote.

List all layouts: whitedeck layouts

title            title-center     title-top        title-bullets
bullets          title-bullets-photo               photo
photo-horizontal photo-vertical   photo-3-up       quote            blank
compare          (virtual: side-by-side bullet columns on Keynote geometry)
title-left       section-left     title-bullets-left   (left-aligned at a 54pt margin)
scope-shot       scope-compare    scope-shot-notes     (annotated screenshot slides)

Annotated screenshot slides carry a Scope: header line, a Tool: logo, bordered screenshots (![border=red label="JS on"](shot.png)), a notes column and a Caption: link; logo: x.png in the front matter paints a logo on every slide; **bold** and [x]{#1db100} colour runs survive into PPTX and Keynote. See examples/scope-demo.md and the skill.

whitedeck build deck.md -f html,pdf,pptx -o out/   # render formats
whitedeck build - -f pptx < deck.md                # stdin
whitedeck build deck.md -o out/board-q3.pptx       # exact file, format from the extension
whitedeck build deck.md -f all --name board-q3     # explicit base name
whitedeck layouts --json                           # machine-readable layout list
whitedeck validate deck.md                         # JSON report, exit 1 on errors
whitedeck init [name]                              # scaffold an example deck

Outputs are named after the deck, not after the input file: the front-matter title (or, without one, the first headline) becomes a slug.

---
title: Q3 Revenue Review
---

→ q3-revenue-review.html, q3-revenue-review.pdf, q3-revenue-review.pptx, q3-revenue-review.key - whatever the markdown file or the stdin pipe was called. Umlauts transliterate (Über Größe → ueber-groesse), slugs are capped at 60 characters on a word boundary. Override with --name <base> or -o <dir>/<file>.<format>. A deck with no title and no input file name (stdin) is an error, not a file called deck.

• Claude skill :skills/whitedeck/SKILL.md ships with the package - including the editorial persona (assertion headlines, max 5 bullets, one chart per slide, everything linked to its data source).
• MCP server :whitedeck-mcp (stdio) exposeswhitedeck_build ,whitedeck_layouts ,whitedeck_validate .whitedeck_build follows the same format rules as the CLI and reportsbuilt andskipped (format, reason, fix):

claude mcp add whitedeck -- whitedeck-mcp

TDD red-to-green, 100% integration tested, zero mocks - tests drive the real Marp, real Chrome, real Keynote.app and a real MCP stdio client:

npm install
npm run gates    # typecheck, lint, test, build
npm run smoke    # build every example with -f all on this OS

MIT (c) 2026 Franz Enzenhofer

Not affiliated with or endorsed by Apple Inc. Keynote is a trademark of Apple Inc. whitedeck contains no Apple assets - only independently measured layout geometry.