FrankenMarkdown — The Monster Markdown Engine

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V0.3.0 Alive on Crates.io

The

Monster

Markdown<br>Engine.

Stitched together from a clean-room parser, LaTeX-grade typesetting, and a<br>hand-rolled PDF writer — one auditable Rust core with<br>zero dependencies that renders<br>Markdown to beautiful self-contained HTML and compact tagged PDF.<br>Natively, and in this very page via WASM. Byte-for-byte identical.

TRY THE PLAYGROUND

GET STARTED

VIEW SOURCE

fmd_render_stream

Live Session

Core Crates

0deps

Engine Dependencies

the core is 100% our Rust

Native ↔ WASM Parity

100%

byte-identical HTML + PDF, gated in CI

CommonMark Ratchet

379

conformance floor that can only rise

WASM Payload

1.5MB gz

fonts, highlighter & PDF writer included

SPECIMEN_001 · LIVE EXPERIMENT

The Operating Theater.

Type Markdown on the left. The actual engine — compiled to WebAssembly,<br>running in a worker in your browser — renders it on the right. Flip the switch<br>to typeset the same document as a PDF. No server. No mock. The monster itself.

fmd_playground

PARITY_100%<br>DETERMINISM_LOCKED

REANIMATING…

Maximize

Sample<br>Showcase<br>Code<br>Tables

HTML<br>PDF

Font

sans<br>serif

Dark CSS

auto<br>disabled

PDF Line №

↓ HTML<br>↓ PDF<br>⚡ Share

source.md<br>0 B

self_contained.html<br>RENDERED_IN_BROWSER

Inline PDF viewing unavailable in this browser

OPEN THE PDF

Diagnostics

⚡ Serverless sharing — the document is the link

Share compresses your Markdown with deflate, base64url-encodes it,<br>and packs it into the # fragment of the URL — like<br>franken-markdown.com/#view=max&zdoc=….<br>Nothing is uploaded, stored, or logged: URL fragments are never even sent to the server, and this<br>site has no backend anyway. Whoever opens your link gets the exact document, decompressed and<br>re-typeset locally by the same wasm engine. Documents up to roughly 30 KB of URL travel well<br>in every modern browser.

Deep links

The playground itself is linkable. Fragment parameters compose:

/#view=max — open the playground maximized, full page

/#fmt=pdf — start on the PDF pane

/#zdoc=… — deflated + base64url document payload

/#doc=… — plain base64url payload (no compression)

The playground needs JavaScript + WebAssembly. The rest of the page works fine without them.

SUBSYSTEM_MAP

One AST. Every Organ.

Parse once; render everywhere. HTML, PDF, and WASM read the same tree and the<br>same typed theme, so the surfaces can never drift apart. Click a stage to dissect it.

markdown<br>file · stdin · string

clean-room parser<br>byte-level scanner

document AST<br>one parse, many bodies

theme model<br>colors · spacing · page

HTML emitter<br>self-contained page

layout + PDF writer<br>Knuth–Plass · tagged

WASM ABI<br>this page, right now

VITAL_ORGANS

Built Different.

Every organ in the render path — parser, highlighter, font reader, line breaker,<br>compressor, PDF writer — was grown in this lab, for this exact workflow.

One AST, Two Bodies

HTML and PDF render from the same parse and the same typed theme. Colors, spacing, code styling, and document rhythm stay coherent across surfaces — structurally, not by convention.

Zero-Dependency Core

No comrak, no syntect, no PDF crates, no regex engine. The engine compiles with zero third-party crates (clap exists only for the CLI), enforced by a CI policy gate. Tiny audit surface, fast builds.

Deterministic Bytes

Fixed input + fixed options = identical output bytes, across runs and operating systems. SOURCE_DATE_EPOCH pins PDF dates; CI diffs repeated renders byte-for-byte. Perfect for reproducible builds and caching.

LaTeX-Grade Typography

Knuth–Plass optimal paragraph breaking, Liang hyphenation, real font metrics, GPOS kerning, GSUB ligatures, and measured-column tables. PDF output that reads like it was typeset, because it was.

Clean-Room Highlighter

Rust, Python, JS/TS, JSON, shell, PowerShell, Go, C/C++, TOML, YAML, SQL, HTML/SVG, CSS, Markdown, and Mermaid — one hand-written highlighting model shared by HTML and PDF. Diagram-shaped ASCII keeps its geometry.

Agent-First CLI

The first command an agent guesses works: fmd README.md. Stdout is data, stderr is diagnostics, exit codes are stable, and capabilities --json, doctor --json, and robot-docs expose the whole contract.

TYPE_LAB

Typeset Like TeX.

Word processors break lines greedily: fill until full, wrap, repeat — and one bad<br>line poisons the paragraph. FrankenMarkdown's PDF path uses the Knuth–Plass<br>total-fit algorithm: it considers every possible set of breakpoints and picks<br>the one that minimizes ugliness across the whole paragraph. This demo runs both<br>algorithms live. Drag the measure and watch the line tinting: the hotter a line, the<br>more its spaces were stretched or squeezed.

Line width

492px measure

Greedy (first-fit) — what most tools do

Knuth–Plass (total-fit) — what fmd does

comfortable spacing<br>stretched<br>abused<br>— hover any line for its adjustment ratio and badness. Same font,...