@momiji-rs/sparkdown

Fast, standards-first CommonMark → HTML — and the fastest drop-in remark-parse — compiled to WASI-free WebAssembly.

• ✅ 100% CommonMark 0.31.2 — all 652 official examples pass through the wasm.
• 🚀 ~0.9 ms to render the 200 KB CommonMark spec — ~5× faster than markdown-it/marked, and faster than rushdown's native build; the native crate does it in ~0.59 ms.
• 🌳 Fastest remark-parse. The /mdast subpath emits a unist/mdast tree that deep-equals mdast-util-from-markdown on all 652 examples — ~80× faster, drop-in for unified / remark / rehype.
• 🪶 Zero dependencies, self-contained. The wasm is base64-inlined, so it works in Node, browsers, bundlers, Deno, Bun, and edge runtimes (Cloudflare Workers, Fastly, Vercel) with no fetch, fs, WASI, or asset configuration.

npm install @momiji-rs/sparkdown

import { toHtml } from "@momiji-rs/sparkdown";

const html = await toHtml("# Hello *world*\n\nWith a [link](https://example.com).");
// <h1>Hello <em>world</em></h1>\n<p>With a <a href="https://example.com">link</a>.</p>\n

Importing has no side effect — the wasm instantiates lazily. For synchronous use, call initSync() once (server-side: Node/Bun/Deno/edge/workers, not the browser main thread) or await ready in browsers:

import { initSync, toHtmlSync } from "@momiji-rs/sparkdown";

initSync(); // sync, idempotent — once, on first use
for (const post of posts) post.html = toHtmlSync(post.markdown); // sync, hot loop

API

| export | signature | notes | | --- | --- | --- | | toHtml | (markdown: string) => Promise<string> | lazily instantiates the wasm | | toHtmlSync | (markdown: string) => string | needs a prior initSync() / await ready | | initSync | () => unknown | sync instantiation (idempotent); server-side only | | ready | PromiseLike<void> | lazily instantiates once awaited | | init | () => Promise<unknown> | async instantiation (idempotent) |

toHtml is also the default export. TypeScript types are bundled.

Extensions — the /gfm and /full subpaths

The package root is pure CommonMark (smallest wasm). Two subpaths add extensions — same engine, a larger wasm, and a toHtml(md, options) that toggles each one per call:

import { toHtml } from "@momiji-rs/sparkdown/gfm";  // + GitHub Flavored Markdown
await toHtml("~~done~~ and www.example.com");
await toHtml(md, { tables: false }); // toggle a flag

import { toHtml } from "@momiji-rs/sparkdown/full"; // + every extension
await toHtml(":::note\n`:tada:` ~~x~~\n:::");       // directives, emoji, … on by default

| subpath | adds | wasm | | --- | --- | --- | | @momiji-rs/sparkdown | — (CommonMark) | ~182 KB | | @momiji-rs/sparkdown/gfm | strikethrough, tasklists, autolinks, tag filter, tables, footnotes | ~239 KB | | @momiji-rs/sparkdown/full | + frontmatter, emoji, definition lists, directives, diagrams, external-link rel, heading ids | ~319 KB | | @momiji-rs/sparkdown/mdast | markdown → mdast tree + a unified remark-parse plugin (see below) | ~440 KB |

A bundler ships only the subpath you import. The . / /gfm / /full entries share the same toHtml / toHtmlSync / initSync / ready / init surface; /mdast adds toMdast and a unified parser plugin.

mdast — the fastest remark-parse

@momiji-rs/sparkdown/mdast emits a full mdast (unist) tree — the exact shape remark-parse produces — as a drop-in, ~80× faster parser for the unified / remark / rehype ecosystem:

import { unified } from "unified";
import sparkdownParse from "@momiji-rs/sparkdown/mdast"; // drop-in remark-parse
import remarkRehype from "remark-rehype";
import rehypeStringify from "rehype-stringify";

await sparkdownParse.ready; // browsers only; Node/Bun/Deno/edge need no await
const html = String(unified()
  .use(sparkdownParse)
  .use(remarkRehype)
  .use(rehypeStringify)
  .processSync(markdown));

Or call it directly — toMdast(md, options) → tree, toHtml(md, options) → HTML (an in-wasm mdast → html render, byte-identical to mdast-util-to-hast + hast-util-to-html). The tree is plain unist objects (not opaque handles), so every remark plugin works unmodified; it deep-equals mdast-util-from-markdown on all 652 CommonMark examples including position. Pass { position: false } for ~2× faster parsing when your plugins don't read source positions.

| export | signature | | --- | --- | | sparkdownParse (default) | unified parser plugin — unified().use(sparkdownParse) | | toMdast / toMdastSync | (markdown, options?) => mdast tree | | toHtml / toHtmlSync | (markdown, options?) => string (in-wasm mdast→html) | | initSync / init / ready | instantiation (as in the other entries) |

How it's built

The package wraps a wasm32-unknown-unknown build of the sparkdown Rust crate via a tiny raw C-ABI (sparkdown_alloc / sparkdown_free / sparkdown_to_html) — no wasm-bindgen. The wasm uses +simd128 (vectorized inline scan + escape) and +bulk-memory (native memory.copy), so it needs a host from ~2021 onward (all current browsers, Node 16+, Deno, Bun, modern edge runtimes).

License

MIT.