@mdgate/html

Convert HTML to Markdown in TypeScript.

@mdgate/html reads .html, .htm, .html4, .html5, .xhtml, .mhtml, and .mht files directly in JavaScript and converts them into GitHub-Flavored Markdown, without Python, native addons, WASM, or a browser engine.

Works in Node.js, Cloudflare Workers, Edge runtimes, and browsers.

npm install @mdgate/html

import { toMarkdown } from '@mdgate/html';

const markdown = await toMarkdown(bytes);

bytes is a Uint8Array, so the page can come from a file upload, a crawl, an HTTP response, a browser file picker, or anywhere else your application gets bytes.

Why @mdgate/html

HTML is the interchange format for saved pages, MHTML archives, and a lot of "export as web page" output from office tools.

@mdgate/html is an HTML reader written for the same runtime as your application:

• Pure TypeScript
• HTML → Markdown locally
• No Python runtime
• No native addons
• No WASM runtime
• Zero third-party runtime dependencies
• Works with raw Uint8Array input
• Detects HTML and MHTML from their contents, not only the filename

What it extracts

@mdgate/html parses the markup, walks the tree, and rebuilds a shared document model.

The converter handles HTML-specific concerns including:

• headings, paragraphs, and block quotes
• bold, italic, strikethrough, and inline code
• links and relative URLs
• ordered, unordered, and nested lists
• tables, including spanning cells
• code blocks
• MHTML / MHT archives (MIME-wrapped HTML)
• XHTML

The output is Markdown that can be searched, indexed, chunked, cached, or passed directly to an AI agent.

Node.js

import { readFile } from 'node:fs/promises';
import { toMarkdown } from '@mdgate/html';

const bytes = new Uint8Array(await readFile('page.html'));
const markdown = await toMarkdown(bytes);

console.log(markdown);

Browser

import { toMarkdown } from '@mdgate/html';

const file = input.files![0];
const bytes = new Uint8Array(await file.arrayBuffer());

const markdown = await toMarkdown(bytes);

Cloudflare Workers and Edge runtimes

import { toMarkdown } from '@mdgate/html';

export default {
  async fetch(request: Request) {
    const bytes = new Uint8Array(await request.arrayBuffer());
    const markdown = await toMarkdown(bytes);

    return new Response(markdown, {
      headers: {
        'content-type': 'text/markdown; charset=utf-8',
      },
    });
  },
};

Format detection

You do not need to trust the file extension.

@mdgate/html recognizes HTML and MHTML from their contents.

const markdown = await toMarkdown(bytes);

A path can still be supplied as a format hint when @mdgate/html is used through @mdgate/converters or a reader composed with @mdgate/core, but the path is never used to read a file from disk.

Compose it with other file readers

@mdgate/html implements the converter interface from @mdgate/core.

import { create } from '@mdgate/core';
import { html } from '@mdgate/html';
import { email } from '@mdgate/email';

const read = create([
  html(),
  email(),
]);

The application still uses one reading interface while each format remains independently installable.

Need more than HTML?

If your application needs to read many different file types, use the complete converter set:

npm install @mdgate/converters

import { toMarkdown } from '@mdgate/converters';

const markdown = await toMarkdown(bytes, {
  path: filename,
});

@mdgate/html is one of the single-format packages in the open-source mdgate/converters project.

For AI agents, the same converter architecture can be used to extend read_file from text files to real-world document formats.

License

MIT