Deckx

deckx

deckx builds a single, self-contained HTML slide deck from one MDX file plus a CSS theme and an optional folder of React components. The HTML is print-ready and converts to PDF via Chrome headless.

Installation

bun init -y  # if you don't already have a package.json initialized
bun add @samuelcolvin/deckx

The npm package is @samuelcolvin/deckx; the installed CLI binary is deckx. npm i / pnpm add work the same way. Inside deck.mdx you always import from "deckx" (a Vite alias, not the npm name).

Project layout

my-deck/
├── deckx.toml          # config: title, theme, tabs, footer, paths (all optional)
├── deck.mdx            # the slides
├── styles.css          # CSS variable overrides (optional)
└── components/         # optional custom React/TSX components
    └── Hello.tsx

bunx deckx dev          # dev server with HMR on http://localhost:5173/
bunx deckx html         # build to ./dist/index.html
bunx deckx pdf          # build HTML, then ./dist/deck.pdf via Chrome headless

html and pdf accept an optional output-path positional - e.g. bunx deckx pdf my-deck.pdf or bunx deckx html out/slides.html. Use --dir <dir> to point at a build directory other than the current one. To convert an existing HTML file to PDF without rebuilding, use bunx deckx html-to-pdf <input.html> <output.pdf>.

deckx.toml

All fields are optional - a deck with only deck.mdx works.

title = "My Deck - April 2026"        # browser tab title

# light | dark | markdown-light | markdown-dark   (default: light)
# "markdown-*" variants render source-style decorations on top:
# heading "#"/"##" prefixes, "**" strong markers, traffic-light dots,
# mono slide counter, diamond bullets.
theme = "light"

# Small footer rendered bottom-right of every slide.
footer = "Confidential - do not share"

# Path to a favicon for the browser tab. .svg / .png / .ico / .jpg.
# Inlined as a data URI so the deck stays self-contained.
favicon = "assets/favicon.svg"

# Path overrides (defaults shown).
mdx = "deck.mdx"
styles = "styles.css"
components = "components"

# Optional tab nav. When present, <Slide tab="..."> highlights the matching tab.
tabs = [
  { id = "intro", label = "Intro" },
  { id = "details", label = "Details" },
]

If tabs is omitted, the tab prop on <Slide> is ignored and slides render with a plain title topbar.

deck.mdx

Standard MDX. Import Slide from "deckx", plus any custom components from ./components/.

import { Slide } from "deckx";
import Hello from "./components/Hello.tsx";

<Slide layout="title" title="Investor Deck / April 2026">

### Section Label

# My Deck

## A subtitle

</Slide>

<Slide tab="intro">

# Hello world

- Bullet one
- Bullet two

<Hello name="friend" />

</Slide>

<Slide layout="statement">

# One big idea.

</Slide>

Do NOT wrap slides in <div className="deck"> - deckx adds it for you.

<Slide> props

All props are optional. A bare <Slide> renders a regular content slide using the deck theme.

layout - structural layout (default 'content')

Picks how the slide arranges its body. Adds a .<value>-slide class to the .slide element so you can target each variant from styles.css.

• 'content' (default) - regular slide. Headings, paragraphs, bullets, code, and tables flow top-down inside .slide-body. Use for the bulk of your deck.
• 'title' - cover / section slide. Bottom-aligns the hero; h1 is 4rem with tight letter-spacing; h2 renders in --accent. Pair with a leading ### Section Label for a mono uppercase eyebrow.
• 'statement' - centered one-liner. The body is centered both vertically and horizontally; h1 is 3.4rem; paragraphs cap at 80% width. Use for transitions between sections or "one bold idea" beats.

theme - color variant (defaults to the deck theme)

Per-slide palette override.

• Omit (or pass 'dark') - the slide inherits the deck-level theme from deckx.toml.
• 'light' - forces a single slide onto the light palette (--bg-light, --color-text-light, --color-heading-light) regardless of the deck theme. Useful when one slide needs to break out - e.g. a screenshot of a light-themed UI on an otherwise dark deck. Adds .light-slide to the slide.

There is no inverse override: on a light deck, theme="dark" has no effect. If you need a single dark slide on a light deck, target it from CSS with a custom id or class.

Other props

• tab - string matching an id from the tabs array in deckx.toml. Replaces the plain topbar title with the tab bar, with this slide's tab highlighted. Clicking any tab in any slide jumps to the first slide whose tab matches. If tabs is not configured, the prop is silently ignored.
• title - plain text rendered in the topbar when tab is not set. Also drives document.title, so the browser tab updates as the active slide changes. Ignored when tab is set.
• space - 'tight' reduces bullet/paragraph spacing (use when a slide is close to overflowing); 'wide' increases padding and line-height (use for slides with very little text where you want generous breathing room).
• fontSize - 'large' bumps body text from 1.15rem to 1.35rem, and h1/h2 proportionally. Useful for slides that need to read from the back of a room.
• id - sets the HTML id on the underlying <section>. Useful for targeting one slide from styles.css (.slide#hero { ... }) without adding a custom class.

MDX gotchas

• Use - (hyphen-minus), never — (em dash).
• Keep blank lines around block elements inside a slide, but not between the last block and the closing </Slide> - MDX misparses a trailing blank.
• ### Section Label at the top of a slide renders as a diamond + uppercase mono label.
• Slides must fit 279.4mm × 157.2mm (16:9). If overflowing, try space="tight" first, then drop content.

Images

Place images in your project (e.g. assets/) and import as ES modules:

import logo from "./assets/logo.png";
<img src={logo} alt="Logo" />

Vite inlines them into the final HTML. The markdown ![alt](path) syntax does not get inlined - always use <img src={imported} />.

Code blocks

Fenced code blocks are syntax-highlighted at build time by Shiki. Tag the fence with a language so tokens get coloured:

```ts
export function greet(name: string): string {
  return `hello, ${name}`;
}
```

All Shiki bundled languages work without any per-deck configuration. Highlighting happens during the build, so the output HTML carries only inline-styled <span>s - no grammar files, no runtime highlighter.

Both a light and a dark theme are emitted into every code block. deckx switches between them automatically based on the slide's effective theme: dark deck themes (dark, markdown-dark) use the dark code theme, and <Slide theme="light"> always shows the light code theme even inside a dark deck. Pick the two themes in deckx.toml:

code_light_theme = "github-light"   # default
code_dark_theme  = "github-dark"    # default

Browse the available themes at https://shiki.style/themes.

Custom components

Any .tsx file in components/ (or wherever deckx.toml components points) can be imported into deck.mdx with a relative path:

// components/Hello.tsx
export default function Hello({ name }: { name: string }) {
  return <p>Hello, {name}!</p>;
}

import Hello from "./components/Hello.tsx";
<Hello name="world" />

React 19 is available. Components see the same CSS variables your styles.css defines, so to stay on-brand, read from variables (color: var(--accent)) rather than hard-coding colors.

Authoring styles.css

The base stylesheet handles all layout, typography, slide dimensions, the topbar, transitions, and the PDF @page setup. styles.css only needs to override CSS variables on :root to set brand tokens.

Variable contract

Backgrounds:

• --bg-deck (default #0d0d0d) - background outside the slide, presenter mode only.
• --bg-slide (default #1a1a1a) - default slide background.
• --bg-light (default #ffffff) - slide bg for light / markdown-light decks and <Slide theme="light">.
• --surface (default #2a2a2a) - inline code background, table headers.

Text:

• --color-text (default white @ 85%) - body text on dark slides.
• --color-heading (default #ffffff) - h1, h2, h4, strong on dark slides.
• --color-muted (default #8f888e) - heading prefixes, slide counter, subdued UI.
• --color-text-light (default #2a2230) - body text on light slides.
• --color-heading-light (default #1a1018) - headings on light slides.

Accents:

• --accent (default #4a9eff) - primary accent: bullets, h3, links, blockquote bar.
• --accent-secondary (default #ff6b6b) - em, link hover.
• --accent-tertiary (default #b388ff) - hr gradient stop.
• --accent-aqua (default #4ad7c5) - inline code text, active tab, topbar tabs.

Fonts:

• --font-body (default system sans stack) - body and headings, unless --font-heading overrides.
• --font-heading (default inherits body) - headings.
• --font-mono (default system mono) - inline code, code blocks, tabs, counter, h3.
• --font-terminal (default inherits body) - body inside .slide-body.

CSS class hooks

For finer control beyond the variable contract, target these classes from styles.css. Most decks won't need them - prefer overriding variables first.

Slide structure:

• .deck-presenter - outermost wrapper. Owns the viewport background and the fit-to-window scaling transform.
• .deck - inner slide stream (direct child of .deck-presenter).
• .slide - a single slide (<section>). Sized 16:9, holds topbar + content + optional footer.
• .slide-topbar - 48px window-chrome bar at the top of every slide.
• .slide-content - padded body wrapper below the topbar (this is what --slide-padding applies to).
• .slide-body - inner MDX content container, descendant of .slide-content.
• .slide-footer - bottom-right footer text, rendered when footer is set in deckx.toml.

Slide modifiers (added to .slide based on props):

• .title-slide - layout="title", bottom-aligned hero.
• .statement-slide - layout="statement", centered hero.
• .light-slide - theme="light", forces the light palette.
• .space-tight / .space-wide - vertical spacing density.
• .font-large - bumps body text size.

Topbar - left (traffic lights + title/tabs):

• .topbar-dots - the traffic-light anchor (clicking jumps to slide 1). Only visible under markdown-* themes.
• .topbar-dot plus .topbar-dot--red / .topbar-dot--yellow / .topbar-dot--green - individual dots.
• .topbar-title - plain title text, shown when <Slide title="..."> is set without a tab.

Topbar - tabs (rendered when <Slide tab="..."> is set and tabs are configured in deckx.toml):

• .topbar-tabs - the tab bar container.
• .topbar-tab-group - per-tab wrapper containing the link plus its leading separator.
• .topbar-tab-sep - the → glyph between tabs.
• .topbar-tab - the tab link.
• .topbar-tab--active - applied to the currently-selected tab.

Topbar - right (prev/next + counter):

• .topbar-nav - container holding the prev/next buttons and slide counter.
• .topbar-nav-btn plus .topbar-nav-prev / .topbar-nav-next - the nav buttons (auto-hidden in print).
• .topbar-nav-counter - the 01/12 slide counter.

Deck-level theme classes (applied to both <html> and .deck-presenter based on theme in deckx.toml):

• .theme-light / .theme-dark / .theme-markdown-light / .theme-markdown-dark

MDX content inside .slide-body renders as plain HTML (h1-h4, p, ul, ol, pre, code, table, blockquote, a, img, hr) - target those tags directly with .slide <tag> selectors rather than expecting deckx to add wrapper classes.

Mapping a brand palette

1. Pick the most distinctive brand color, assign to --accent. Pick a warm counterpoint as --accent-secondary.
2. Pick a slightly off-white for --color-heading (pure white reads sterile under projector light).
3. Pick a tinted dark for --bg-slide (pure black is harsh).
4. For light slides, pick a tinted light bg (cream, eggshell, lavender - not pure white) plus a near-black text color → --bg-light / --color-heading-light / --color-text-light.
5. For custom fonts, self-host woff2 files in assets/ and declare them with @font-face in styles.css, then point --font-body / --font-mono at the family. Do not use @import url(...) from Google Fonts - CSS spec requires @import to come before all other statements, which Vite's CSS bundling routinely violates when concatenating the base stylesheet with yours. @font-face can appear anywhere. Use Google Webfonts Helper to download woff2 files; Vite inlines them into the deck, keeping it self-contained for offline / PDF export.

@font-face {
  font-family: 'YourFont';
  src: url('./assets/YourFont-Regular.woff2') format('woff2');
  font-weight: 400;
  font-display: swap;
}

:root {
  --bg-slide: #...;       /* tinted dark */
  --bg-light: #...;       /* tinted light */
  --surface: #...;

  --color-heading: #...;  /* off-white */
  --color-text: rgba(...);
  --color-heading-light: #...;
  --color-text-light: #...;

  --accent: #...;            /* signature brand color */
  --accent-secondary: #...;  /* warm counterpoint */

  --font-body: 'YourFont', system-ui, sans-serif;
  --font-mono: 'YourFontMono', ui-monospace, monospace;
}

Building & PDF

bunx deckx pdf is the easy path: it builds the HTML, prints the exact Chrome command it's about to run, then runs it. Output lands at ./dist/deck.pdf.

If Chrome / Chromium can't be found, copy the printed command and run it yourself with the right binary path. On Linux deckx auto-detects google-chrome, google-chrome-stable, chromium, or chromium-browser.

Paper size in the printed command matches the slide dimensions (11in × 6.1875in = 16:9). If you override --slide-width / --slide-height in styles.css, edit the --paper-* flags to match before running.

To spot-check the PDF (requires pdftoppm from poppler):

mkdir -p ./tmp && pdftoppm -r 100 ./dist/deck.pdf ./tmp/page -png

One PNG per slide lands in ./tmp/, gitignore that path.

Source: pydantic/talks — distributed by TomeVault.