Install

npm install @wasm-fmt/markdown

npx jsr add @fmt/markdown

Usage

Node.js / Deno / Bun / Bundler

import { format } from "@wasm-fmt/markdown";

const input = `#  Hello wasm-fmt

1. markdown
2. clang-format
2. gofmt
2. ruff_fmt
`;

const formatted = format(input, {
	// config
});
console.log(formatted);

Web

For web environments, you need to initialize WASM module manually:

import init, { format } from "@wasm-fmt/markdown/web";

await init();

const input = `#  Hello wasm-fmt

1. markdown
2. clang-format
2. gofmt
2. ruff_fmt
`;

const formatted = format(input);
console.log(formatted);

Embedded code blocks

The Bridge experiment formats Markdown itself, but does not expose the previous synchronous set_format_code_block JavaScript callback. Host callbacks are outside the current Bridge ABI. Code blocks are therefore preserved unless the Markdown formatter can handle them without a host callback. A host-neutral embedded-formatting design will be considered separately.

Vite

import init, { format } from "@wasm-fmt/markdown/vite";

await init();
// ...

Or use the ./bundler entry with vite-plugin-wasm

import { format } from "@wasm-fmt/markdown/bundler";

Entry Points

• . - Auto-detects environment (Node.js uses node, Webpack uses bundler, default is ESM)
• ./node - Node.js environment (no init required)
• ./esm - ESM environments like Deno (no init required)
• ./bundler - Bundlers like Webpack (no init required)
• ./web - Web browsers (requires manual init)
• ./vite - Vite bundler (requires manual init)

Credits

Thanks to:

• The dprint-plugin-markdown project

Embedded languages

Bridge v1 can ask the host to format code fences and YAML front matter. Pass { onFormatEmbedded } as the third argument to format, or register Markdown in createFormatterContext() from @wasm-fmt/runtime. The callback receives { source, filename, lineWidth? } and synchronously returns replacement text, undefined to skip, or throws. Virtual filenames such as embedded.py and embedded.go identify the target language; custom tags config mappings are respected. Target formatters must already be initialized.

An unavailable language is left without an external replacement. A callback failure fails the whole format call, including front matter; the instance can be used again afterward. The callback is separate from formatter configuration and registered config handles. Bundler and ESM entries use import source to instantiate the host-enabled Wasm; use Web/Vite entries if the toolchain does not support source-phase Wasm imports.