micromark

Markdown parser.

Note: this is the micromark package from the micromark monorepo. See the monorepo readme for more on the project. See this readme for how to use it.

Feature highlights

• [x] compliant (100% to CommonMark)
• [x] extensions (100% GFM, 100% MDX.js, directives, frontmatter, math)
• [x] safe (by default)
• [x] robust (±2k tests, 100% coverage, fuzz testing)
• [x] small (smallest CM parser at ±14kb)

Contents

• When should I use this?
• What is this?
• Install
• Use
• API
  • micromark(value[, encoding][, options])
  • stream(options?)
  • Options
• Types
• Compatibility
• Security
• Contribute
• Sponsor
• License

When should I use this?

• If you just want to turn markdown into HTML (with maybe a few extensions)
• If you want to do really complex things with markdown

See § Comparison for more info

What is this?

micromark is an open source markdown parser written in JavaScript. It’s implemented as a state machine that emits concrete tokens, so that every byte is accounted for, with positional info. It then compiles those tokens directly to HTML, but other tools can take the data and for example build an AST which is easier to work with (mdast-util-to-markdown).

While most markdown parsers work towards compliancy with CommonMark (or GFM), this project goes further by following how the reference parsers (cmark, cmark-gfm) work, which is confirmed with thousands of extra tests.

Other than CommonMark and GFM, micromark also supports common extensions to markdown such as MDX, math, and frontmatter.

These npm packages have a sibling project in Rust: markdown-rs.

• to learn markdown, see this cheatsheet and tutorial
• for more about us, see unifiedjs.com
• for updates, see Twitter
• for questions, see Discussions
• to help, see contribute and sponsor below

Install

This package is ESM only. In Node.js (version 16+), install with npm:

npm install micromark

In Deno with esm.sh:

import {micromark} from 'https://esm.sh/micromark@3'

In browsers with esm.sh:

<script type="module">
  import {micromark} from 'https://esm.sh/micromark@3?bundle'
</script>

Use

Typical use (buffering):

import {micromark} from 'micromark'

console.log(micromark('## Hello, *world*!'))

Yields:

<h2>Hello, <em>world</em>!</h2>

You can pass extensions (in this case micromark-extension-gfm):

import {micromark} from 'micromark'
import {gfmHtml, gfm} from 'micromark-extension-gfm'

const value = '* [x] [email protected] ~~strikethrough~~'

const result = micromark(value, {
  extensions: [gfm()],
  htmlExtensions: [gfmHtml()]
})

console.log(result)

Yields:

<ul>
<li><input checked="" disabled="" type="checkbox"> <a href="mailto:[email protected]">[email protected]</a> <del>strikethrough</del></li>
</ul>

Streaming interface:

import {createReadStream} from 'node:fs'
import {stream} from 'micromark/stream'

createReadStream('example.md')
  .on('error', handleError)
  .pipe(stream())
  .pipe(process.stdout)

function handleError(error) {
  // Handle your error here!
  throw error
}

API

micromark core has two entries in its export map: micromark and micromark/stream.

micromark exports the identifier micromark. micromark/stream exports the identifier stream. There are no default exports.

The export map supports the development condition. Run node --conditions development module.js to get instrumented dev code. Without this condition, production code is loaded. See § Size & debug for more info.

micromark(value[, encoding][, options])

Compile markdown to HTML.

Note: which encodings are supported depends on the engine. For info on Node.js, see WHATWG supported encodings.

Parameters

• value (string or Uint8Array) — markdown to parse
• encoding (string, default: 'utf8') — character encoding to understand value as when it’s a Uint8Array
• options (Options, optional) — configuration

Returns

Compiled HTML (string).

stream(options?)

Create a duplex (readable and writable) stream.

Some of the work to parse markdown can be done streaming, but in the end buffering is required.

micromark does not handle errors for you, so you must handle errors on whatever streams you pipe into it. As markdown does not know errors, micromark itself does not emit errors.

Parameters

• options (Options, optional) — configuration

Returns

Duplex stream.

Options

Configuration (TypeScript type).

Fields

allowDangerousHtml

Whether to allow (dangerous) HTML (boolean, default: false).

The default is false, which still parses the HTML according to CommonMark but shows the HTML as text instead of as elements.

Pass true for trusted content to get actual HTML elements. See § Security.

allowDangerousProtocol

Whether to allow dangerous protocols in links and images (boolean, default: false).

The default is false, which drops URLs in links and images that use dangerous protocols.

Pass true for trusted content to support all protocols.

URLs that have no protocol (which means it’s relative to the current page, such as ./some/page.html) and URLs that have a safe protocol (for images: http, https; for links: http, https, irc, ircs, mailto, xmpp), are safe. All other URLs are dangerous and dropped. See § Security.

defaultLineEnding

Default line ending to use when compiling to HTML, for line endings not in value ('\r', '\n', or '\r\n'; default: first line ending or '\n').

Generally, micromark copies line endings (\r, \n, \r\n) in the markdown document over to the compiled HTML. In some cases, such as > a, CommonMark requires that extra line endings are added: <blockquote>\n<p>a</p>\n</blockquote>.

To create that line ending, the document is checked for the first line ending that is used. If there is no line ending, defaultLineEnding is used. If that isn’t configured, \n is used.

extensions

Array of syntax extensions (Array<SyntaxExtension>, default: []). See § Extensions.

htmlExtensions

Array of syntax extensions (Array<HtmlExtension>, default: []). See § Extensions.

Types

This package is fully typed with TypeScript. It exports the additional type Options.

Compatibility

Projects maintained by the unified collective are compatible with maintained versions of Node.js.

When we cut a new major release, we drop support for unmaintained versions of Node. This means we try to keep the current release line, micromark@4, compatible with Node.js 16.

Security

This package is safe. See security.md in micromark/.github for how to submit a security report.

Contribute

See contributing.md in micromark/.github for ways to get started. See support.md for ways to get help.

This project has a code of conduct. By interacting with this repository, organisation, or community you agree to abide by its terms.

Sponsor

Support this effort and give back by sponsoring on OpenCollective!

License

MIT © Titus Wormer