# @logue/markdown-wasm
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[](https://www.npmjs.com/package/@logue/markdown-wasm)
[](https://uiwjs.github.io/npm-unpkg/#/pkg/@logue/markdown-wasm/file/README.md)
[](https://www.npmjs.com/package/@logue/markdown-wasm)
[](https://gitpod.io/#https://github.com/logue/@logue/markdown-wasm)
[](https://twitter.com/logue256)
Very fast Markdown parser & HTML renderer implemented in WebAssembly
- Zero dependencies (87.83 kB gzipped without minify.)
- Portable & safe (WASM executes in isolated memory and can run almost anywhere)
- [Simple API](#api)
- [Very fast](#benchmarks)
- Based on [md4c](http://github.com/mity/md4c) — compliant to the CommonMark specification
## Install
```sh
yarn add markdown-wasm
```
## Examples
ES module with WASM loaded separately
```js
import { ready, parse } from './dist/markdown.es.js';
await ready();
console.log(parse('# hello\n*world*'));
```
Web browser
```html
```
## CLI Usage
```shell
md2html [FILE] [-o FILE] [-t NAME]
```
### Options
| switch | type | description |
| ------------------ | ------- | ----------- | --------------------------------------------------------- |
| `--version` | boolean | | Show version number |
| `--help` | boolean | | Show help |
| `-o`, `--output` | string | | Output file path |
| `-t`, `--template` | string | `default` | Template name |
| `--toc-min` | number | `2` | Minimum heading level to include in the table of contents |
| `--toc-max` | number | `4` | Maximum heading level to include in the table of contents |
| `--html` | boolean | `false` | Allow HTML in the input |
### CLI Examples
Convert input.md to output.html.
```shell
md2html input.md -o output.html
cat input.md | md2html > output.html Convert input.md to output.html.
```
## API
```ts
/** Options for the parse function */
export interface ParseOptions {
/** Customize parsing. Defaults to ParseFlags.DEFAULT */
parseFlags?: ParseFlagsType | number;
/** Enable Debug log. Default is false */
debug?: boolean;
/** Use xhtml format. Default is true. */
xhtml?: boolean;
/** Output special characters as entity reference characters */
verbatimEntities: boolean;
/** Allow "javascript:" in links */
allowJSURIs?: boolean;
/** Disable anchor tag in headlines. Defaults to `false` */
disableHeadlineAnchors?: boolean;
/**
* bytes=true causes parse() to return the result as a Uint8Array instead of a string.
*
* The returned Uint8Array is only valid until the next call to parse().
* If you need to keep the returned data around, call Uint8Array.slice() to make a copy,
* as each call to parse() uses the same underlying memory.
*
* This only provides a performance benefit when you never need to convert the output
* to a string. In most cases you're better off leaving this unset or false.
*/
bytes?: boolean;
/**
* Optional callback which if provided is called for each code block.
* langname holds the "language tag", if any, of the block.
*
* The returned value is inserted into the resulting HTML verbatim, without HTML escaping.
* Thus, you should take care of properly escaping any special HTML characters.
*
* If the function returns null or undefined, or an exception occurs, the body will be
* included as-is after going through HTML escaping.
*
* Note that use of this callback has an adverse impact on performance as it casues
* calls and data to be bridged between WASM and JS on every invocation.
*/
onCodeBlock?: (
langname: string,
body: Uint8Array
) => Uint8Array | string | null;
}
/** ParseFlags */
export declare const ParseFlags: {
/** In TEXT, collapse non-trivial whitespace into single ' ' */
readonly COLLAPSE_WHITESPACE: 0x0001;
/** Do not require space in ATX headers ( ###header ) */
readonly PERMISSIVE_ATX_HEADERS: 0x0002;
/** Recognize URLs as links even without <...> */
readonly PERMISSIVE_URL_AUTO_LINKS: 0x0004;
/** Recognize e-mails as links even without <...> */
readonly PERMISSIVE_EMAIL_AUTO_LINKS: 0x0008;
/** Disable indented code blocks. (Only fenced code works) */
readonly NO_INDENTED_CODE_BLOCKS: 0x0010;
/** Disable raw HTML blocks. */
readonly NO_HTML_BLOCKS: 0x0020;
/** Disable raw HTML (inline). */
readonly NO_HTML_SPANS: 0x0040;
/** Enable tables extension. */
readonly TABLES: 0x0100;
/** Enable strikethrough extension. */
readonly STRIKETHROUGH: 0x0200;
/** Enable WWW autolinks (without proto; just 'www.') */
readonly PERMISSIVE_WWW_AUTOLINKS: 0x0400;
/** Enable task list extension. */
readonly TASK_LISTS: 0x0800;
/** Enable $ and $$ containing LaTeX equations. */
readonly LATEX_MATH_SPANS: 0x1000;
/** Enable wiki links extension. */
readonly WIKI_LINKS: 0x2000;
/** Enable underline extension (disables '_' for emphasis) */
readonly UNDERLINE: 0x4000;
readonly PERMISSIVE_AUTOLINKS: 0x0008 | 0x0004 | 0x400; // PERMISSIVE_EMAIL_AUTO_LINKS | PERMISSIVE_URL_AUTO_LINKS | PERMISSIVE_WWW_AUTOLINKS
readonly NO_HTML: 0x0020 | 0x0040; // NO_HTML_BLOCKS | NO_HTML_SPANS
/** Default flags */
readonly DEFAULT: 0x0001 | 0x0002 | 0x0004 | 0x0200 | 0x0100 | 0x0800; // COLLAPSE_WHITESPACE | PERMISSIVE_ATX_HEADERS | PERMISSIVE_URL_AUTO_LINKS | STRIKETHROUGH | TABLES | TASK_LISTS
/* Convenient sets of flags corresponding to well-known Markdown dialects.
*
* Note we may only support subset of features of the referred dialect.
* The constant just enables those extensions which bring us as close as
* possible given what features we implement.
*
* ABI compatibility note: Meaning of these can change in time as new
* extensions, bringing the dialect closer to the original, are implemented.
*/
readonly DIALECT_COMMONMARK: 0;
/** Github Style */
readonly DIALECT_GITHUB: 0x0008 | 0x0004 | 0x400 | 0x0100 | 0x0200 | 0x0800; // PERMISSIVE_AUTO_LINKS | TABLES | STRIKETHROUGH | TASK_LISTS
```
See [`markdown.d.ts`](markdown.d.ts)
## Building from source
Install latest emscripten to your environment.
```sh
pnpm install
pnpm build-wasm
pnpm build-bundle
```
## Benchmarks
The [`test/benchmark`](test/benchmark) directory contain a benchmark suite which you can
run yourself. It tests a few popular markdown parser-renderers by parsing & rendering a bunch
of different sample markdown files.
To regenerate the benchmark CSV and SVG graphs from the repository root:
```sh
pnpm install
pnpm benchmark
pnpm benchmark:graph
```
### Test Environments
MacBook Pro M5 running on macOS Tahoe 26.4.1, NodeJS v24.15.0
| Name | Version |
| --------------------------------------------------------- | ------- |
| [commonmark](https://github.com/commonmark/commonmark.js) | 0.31.2 |
| [markdown-it](https://github.com/markdown-it/markdown-it) | 14.1.1 |
| [marked](https://github.com/markedjs/marked) | 18.0.2 |
| [micromark](https://github.com/micromark/micromark) | 4.0.2 |
| [remarkable](https://github.com/jonschlinkert/remarkable) | 2.0.1 |
| [showdown](https://github.com/showdownjs/showdown) | 2.1.0 |
### Average ops/second
Ops/second represents how many times a library is able to parse markdown and render HTML
during a second, on average across all sample files.
### Average throughput
Throughput is the average amount of markdown data processed during a second while both parsing
and rendering to HTML. The statistics does not include HTML generated but only bytes of markdown
source text parsed.
### Min–max parse time
This graph shows the spread between the fastest and slowest parse-and-render operations
for each library. Lower numbers are better.
See [`test/benchmark`](test/benchmark#readme) for more information.
## See Also
- [vue-markdown-wasm](https://github.com/logue/vue-markdown-wasm) - Markdown-wasm for Vue2 and 3 component.
## License
[LICENSE](LICENSE)
(c) 2019-2020 Rasmus Andersson
(c) 2023-2025 Masashi Yoshikawa