html-to-markdown

High-performance HTML to Markdown converter for Node.js and Bun with full TypeScript support. This package wraps native @kreuzberg/html-to-markdown-node bindings and provides a type-safe API.

Installation

npm install @kreuzberg/html-to-markdown

Requires Node.js 18+ or Bun. Native bindings provide superior performance.

npm:

npm install @kreuzberg/html-to-markdown

pnpm:

pnpm add @kreuzberg/html-to-markdown

yarn:

yarn add @kreuzberg/html-to-markdown

bun:

bun add @kreuzberg/html-to-markdown

Alternatively, use the WebAssembly version for browser/edge environments:

npm install @kreuzberg/html-to-markdown-wasm

Performance Snapshot

Apple M4 • Real Wikipedia documents • convert() (TypeScript (Node.js))

| Document | Size | Latency | Throughput | | -------- | ---- | ------- | ---------- | | Lists (Timeline) | 129KB | 0.58ms | 222 MB/s | | Tables (Countries) | 360KB | 1.89ms | 190 MB/s | | Mixed (Python wiki) | 656KB | 4.21ms | 156 MB/s |

Quick Start

Basic conversion:

import { convert } from '@kreuzberg/html-to-markdown';

const result = convert('<h1>Hello World</h1>');
const markdown: string = result.content;
console.log(markdown); // # Hello World

With conversion options:

import { convert, ConversionOptions } from '@kreuzberg/html-to-markdown';

const options: ConversionOptions = {
  headingStyle: 'atx',
  listIndentWidth: 2,
  wrap: true,
};

const result = convert('<h1>Title</h1><p>Content</p>', options);
const markdown = result.content;

API Reference

Core Function

convert(html: string, options?: ConversionOptions, visitor?: Visitor): ConversionResult

Converts HTML to Markdown. Returns a ConversionResult object with all results in a single call.

import { convert, ConversionOptions } from '@kreuzberg/html-to-markdown';

const result = convert(html);
const markdown  = result.content;    // Converted Markdown string
const metadata  = result.metadata;   // Metadata (when extractMetadata: true)
const tables    = result.tables;     // Structured table data (when extractTables: true)
const document  = result.document;   // Document-level info
const images    = result.images;     // Extracted images
const warnings  = result.warnings;   // Any conversion warnings

Options

ConversionOptions – Key configuration fields:

• heading_style: Heading format ("underlined" | "atx" | "atx_closed") — default: "underlined"
• list_indent_width: Spaces per indent level — default: 2
• bullets: Bullet characters cycle — default: "*+-"
• wrap: Enable text wrapping — default: false
• wrap_width: Wrap at column — default: 80
• code_language: Default fenced code block language — default: none
• extract_metadata: Enable metadata extraction into result.metadata — default: false
• extract_tables: Enable structured table extraction into result.tables — default: false
• output_format: Output markup format ("markdown" | "djot" | "plain") — default: "markdown"

Djot Output Format

The library supports converting HTML to Djot, a lightweight markup language similar to Markdown but with a different syntax for some elements. Set output_format to "djot" to use this format.

Syntax Differences

| Element | Markdown | Djot | |---------|----------|------| | Strong | **text** | *text* | | Emphasis | *text* | _text_ | | Strikethrough | ~~text~~ | {-text-} | | Inserted/Added | N/A | {+text+} | | Highlighted | N/A | {=text=} | | Subscript | N/A | ~text~ | | Superscript | N/A | ^text^ |

Example Usage

import { convert, ConversionOptions } from '@kreuzberg/html-to-markdown';

const html = "<p>This is <strong>bold</strong> and <em>italic</em> text.</p>";

// Default Markdown output
const markdown = convert(html);
// Result: "This is **bold** and *italic* text."

// Djot output
const djot = convert(html, { outputFormat: 'djot' });
// Result: "This is *bold* and _italic_ text."

Djot's extended syntax allows you to express more semantic meaning in lightweight text, making it useful for documents that require strikethrough, insertion tracking, or mathematical notation.

Plain Text Output

Set output_format to "plain" to strip all markup and return only visible text. This bypasses the Markdown conversion pipeline entirely for maximum speed.

import { convert } from '@kreuzberg/html-to-markdown';

const html = "<h1>Title</h1><p>This is <strong>bold</strong> and <em>italic</em> text.</p>";

const plain = convert(html, { outputFormat: 'plain' });
// Result: "Title\n\nThis is bold and italic text."

Plain text mode is useful for search indexing, text extraction, and feeding content to LLMs.

Metadata Extraction

The metadata extraction feature enables comprehensive document analysis during conversion. Extract document properties, headers, links, images, and structured data in a single pass — all via the standard convert() function.

Use Cases:

• SEO analysis – Extract title, description, Open Graph tags, Twitter cards
• Table of contents generation – Build structured outlines from heading hierarchy
• Content migration – Document all external links and resources
• Accessibility audits – Check for images without alt text, empty links, invalid heading hierarchy
• Link validation – Classify and validate anchor, internal, external, email, and phone links

Zero Overhead When Disabled: Metadata extraction adds negligible overhead and happens during the HTML parsing pass. Pass extract_metadata: true in ConversionOptions to enable it; the result is available at result.metadata.

Example: Quick Start

import { convert } from '@kreuzberg/html-to-markdown';

const html = '<h1>Article</h1><img src="test.jpg" alt="test">';
const result = convert(html, { extractMetadata: true });

console.log(result.content);                      // Converted Markdown
console.log(result.metadata?.document?.title);    // Document title
console.log(result.metadata?.headers);            // All h1-h6 elements
console.log(result.metadata?.links);              // All hyperlinks
console.log(result.metadata?.images);             // All images with alt text
console.log(result.metadata?.structuredData);     // JSON-LD, Microdata, RDFa

Visitor Pattern

The visitor pattern enables custom HTML→Markdown conversion logic by providing callbacks for specific HTML elements during traversal. Pass a visitor as the third argument to convert().

Use Cases:

• Custom Markdown dialects – Convert to Obsidian, Notion, or other flavors
• Content filtering – Remove tracking pixels, ads, or unwanted elements
• URL rewriting – Rewrite CDN URLs, add query parameters, validate links
• Accessibility validation – Check alt text, heading hierarchy, link text
• Analytics – Track element usage, link destinations, image sources

Supported Visitor Methods: 40+ callbacks for text, inline elements, links, images, headings, lists, blocks, and tables.

Example: Quick Start

import { convert, type Visitor, type NodeContext, type VisitResult } from '@kreuzberg/html-to-markdown';

const visitor: Visitor = {
  visitLink(ctx: NodeContext, href: string, text: string, title?: string): VisitResult {
    // Rewrite CDN URLs
    if (href.startsWith('https://old-cdn.com')) {
      href = href.replace('https://old-cdn.com', 'https://new-cdn.com');
    }
    return { type: 'custom', output: `[${text}](${href})` };
  },

  visitImage(ctx: NodeContext, src: string, alt?: string, title?: string): VisitResult {
    // Skip tracking pixels
    if (src.includes('tracking')) {
      return { type: 'skip' };
    }
    return { type: 'continue' };
  },
};

const html = '<a href="https://old-cdn.com/file.pdf">Download</a>';
const result = convert(html, {}, visitor);
const markdown = result.content;

Examples

Links

• GitHub: github.com/kreuzberg-dev/html-to-markdown

• npm: npmjs.com/@kreuzberg/html-to-markdown-node

• WASM: npmjs.com/@kreuzberg/html-to-markdown-wasm

• Kreuzberg Ecosystem: kreuzberg.dev

• Discord: discord.gg/pXxagNK2zN

Contributing

We welcome contributions! Please see our Contributing Guide for details on:

• Setting up the development environment
• Running tests locally
• Submitting pull requests
• Reporting issues

All contributions must follow our code quality standards (enforced via pre-commit hooks):

• Proper test coverage (Rust 95%+, language bindings 80%+)
• Formatting and linting checks
• Documentation for public APIs

License

MIT License – see LICENSE.

Support

If you find this library useful, consider sponsoring the project.

Have questions or run into issues? We're here to help:

• GitHub Issues: github.com/kreuzberg-dev/html-to-markdown/issues
• Discussions: github.com/kreuzberg-dev/html-to-markdown/discussions
• Discord Community: discord.gg/pXxagNK2zN