Project: syntax-tree/mdast-util-to-markdown

Package: mdast-util-to-markdown@1.5.0

  1. Dependents: 0
  2. mdast utility to serialize markdown
  1. markdown 154
  2. util 145
  3. utility 141
  4. unist 132
  5. mdast 88
  6. tree 44
  7. ast 37
  8. mdast-util 30
  9. syntax 28
  10. stringify 19
  11. markup 18
  12. compile 14
  13. serialize 12


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mdast utility that turns a syntax tree into markdown.


What is this?

This package is a utility that takes an mdast syntax tree as input and turns it into serialized markdown.

This utility is a low level project. It’s used in remark-stringify, which focusses on making it easier to transform content by abstracting these internals away.

When should I use this?

If you want to handle syntax trees manually, use this. For an easier time processing content, use the remark ecosystem instead.

You can combine this utility with other utilities to add syntax extensions. Notable examples that deeply integrate with it are mdast-util-gfm, mdast-util-mdx, mdast-util-frontmatter, mdast-util-math, and mdast-util-directive.


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

npm install mdast-util-to-markdown

In Deno with esm.sh:

import {toMarkdown} from 'https://esm.sh/mdast-util-to-markdown@2'

In browsers with esm.sh:

<script type="module">
  import {toMarkdown} from 'https://esm.sh/mdast-util-to-markdown@2?bundle'


Say our module example.js looks as follows:

import {toMarkdown} from 'mdast-util-to-markdown'

/** @type {import('mdast').Root} */
const tree = {
  type: 'root',
  children: [
      type: 'blockquote',
      children: [
        {type: 'thematicBreak'},
          type: 'paragraph',
          children: [
            {type: 'text', value: '- a\nb !'},
              type: 'link',
              url: 'example.com',
              children: [{type: 'text', value: 'd'}]


…now running node example.js yields:

> ***
> \- a
> b \![d](example.com)

πŸ‘‰ Note: observe the properly escaped characters which would otherwise turn into a list and image respectively.


This package exports the identifiers defaultHandlers and toMarkdown. There is no default export.

toMarkdown(tree[, options])

Turn an mdast syntax tree into markdown.


Serialized markdown representing tree (string).


Default (CommonMark) handlers (Handlers).


Construct names for things generated by mdast-util-to-markdown (TypeScript type).

This is an enum of strings, each being a semantic label, useful to know when serializing whether we’re for example in a double (") or single (') quoted title.

type ConstructName = ConstructNameMap[keyof ConstructNameMap]


Interface of registered constructs (TypeScript type).

interface ConstructNameMap { /* see code */ }

When working on extensions that use new constructs, extend the corresponding interface to register its name:

declare module 'mdast-util-to-markdown' {
  interface ConstructNameMap {
    // Register a new construct name (value is used, key should match it).
    gfmStrikethrough: 'gfmStrikethrough'


Handle a particular node (TypeScript type).


Serialized markdown representing node (string).


Handle particular nodes (TypeScript type).

Each key is a node type (Node['type']), each value its corresponding handler (Handle).

type Handlers = Record<Node['type'], Handle>


Info on the surrounding of the node that is serialized (TypeScript type).



How to join two blocks (TypeScript type).

β€œBlocks” are typically joined by one blank line. Sometimes it’s nicer to have them flush next to each other, yet other times they cannot occur together at all.

Join functions receive two adjacent siblings and their parent and what they return defines how many blank lines to use between them.


How many blank lines to use between the siblings (boolean, number, optional).

Where true is as passing 1 and false means the nodes cannot be joined by a blank line, such as two adjacent block quotes or indented code after a list, in which case a comment will be injected to break them up:

> Quote 1


> Quote 2

πŸ‘‰ Note: abusing this feature will break markdown. One such example is when returning 0 for two paragraphs, which will result in the text running together, and in the future to be seen as one paragraph.


Map function to pad a single line (TypeScript type).


Padded line (string).


Configuration (TypeScript type).


The following fields influence how markdown is serialized.


Marker to use for bullets of items in unordered lists ('*', '+', or '-', default: '*').

There are three cases where the primary bullet cannot be used:


Marker to use in certain cases where the primary bullet doesn’t work ('*', '+', or '-', default: '-' when bullet is '*', '*' otherwise).

Cannot be equal to bullet.


Marker to use for bullets of items in ordered lists ('.' or ')', default: '.').

There is one case where the primary bullet for ordered items cannot be used:


Whether to add the same number of number signs (#) at the end of an ATX heading as the opening sequence (boolean, default: false).


Marker to use for emphasis ('*' or '_', default: '*').


Marker to use for fenced code ('`' or '~', default: '`').


Whether to use fenced code always (boolean, default: true). The default is to use fenced code if there is a language defined, if the code is empty, or if it starts or ends in blank lines.


Whether to increment the counter of ordered lists items (boolean, default: true).


How to indent the content of list items ('mixed', 'one', or 'tab', default: 'one'). Either with the size of the bullet plus one space (when 'one'), a tab stop ('tab'), or depending on the item and its parent list ('mixed', uses 'one' if the item and list are tight and 'tab' otherwise).


Marker to use for titles ('"' or "'", default: '"').

Whether to always use resource links (boolean, default: false). The default is to use autolinks (<https://example.com>) when possible and resource links ([text](url)) otherwise.


Marker to use for thematic breaks ('*', '-', or '_', default: '*').


Number of markers to use for thematic breaks (number, default: 3, min: 3).


Whether to add spaces between markers in thematic breaks (boolean, default: false).


Whether to use setext headings when possible (boolean, default: false). The default is to always use ATX headings (# heading) instead of setext headings (heading\n=======). Setext headings cannot be used for empty headings or headings with a rank of three or more.


Marker to use for strong ('*' or '_', default: '*').


Whether to join definitions without a blank line (boolean, default: false).

The default is to add blank lines between any flow (β€œblock”) construct. Turning this option on is a shortcut for a Join function like so:

function joinTightDefinitions(left, right) {
  if (left.type === 'definition' && right.type === 'definition') {
    return 0

Handle particular nodes (Handlers, optional).


How to join blocks (Array<Join>, optional).


Schemas that define when characters cannot occur (Array<Unsafe>, optional).


List of extensions (Array<Options>, default: []). Each extension is an object with the same interface as Options itself.


Configuration passed to state.safe (TypeScript type).



Info passed around about the current state (TypeScript type).



Track positional info in the output (TypeScript type).

This info isn’t used yet but such functionality will allow line wrapping, source maps, etc.



Schema that defines when a character cannot occur (TypeScript type).


List of extensions


Markdown is serialized according to CommonMark but care is taken to format in such a way that the resulting markdown should work with most markdown parsers. Extensions can add support for custom syntax.

Syntax tree

The syntax tree is mdast.


This package is fully typed with TypeScript. It exports the additional types ConstructName, ConstructNameMap, Handle, Handlers, Info, Join, Map, Options, SafeConfig, State, and Unsafe.


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, mdast-util-to-markdown@^2, compatible with Node.js 16.


mdast-util-to-markdown will do its best to serialize markdown to match the syntax tree, but there are several cases where that is impossible. It’ll do its best, but complete roundtripping is impossible given that any value could be injected into the tree.

As markdown is sometimes used for HTML, and improper use of HTML can open you up to a cross-site scripting (XSS) attack, use of mdast-util-to-markdown and parsing it again later could potentially be unsafe. When parsing markdown afterwards and then going to HTML, use something like hast-util-sanitize to make the tree safe.


See contributing.md in syntax-tree/.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, organization, or community you agree to abide by its terms.


MIT Β© Titus Wormer