How to load Markdown

Markdown is a lightweight markup language for creating formatted text using a plain-text editor.

Here we cover how to load Markdown documents into LangChain Document objects that we can use downstream.

We will cover:

• Basic usage;
• Parsing of Markdown into elements such as titles, list items, and text.

LangChain implements an UnstructuredLoader class.

Prerequisites

This guide assumes familiarity with the following concepts:

• Documents
• Document Loaders

Installation

npm

npm i @langchain/community @langchain/core

yarn

yarn add @langchain/community @langchain/core

pnpm

pnpm add @langchain/community @langchain/core

Setup

Although Unstructured has an open source offering, you’re still required to provide an API key to access the service. To get everything up and running, follow these two steps:

1. Download & start the Docker container:

docker run -p 8000:8000 -d --rm --name unstructured-api downloads.unstructured.io/unstructured-io/unstructured-api:latest --port 8000 --host 0.0.0.0

1. Get a free API key & API URL here, and set it in your environment (as per the Unstructured website, it may take up to an hour to allocate your API key & URL.):

export UNSTRUCTURED_API_KEY="..."
# Replace with your `Full URL` from the email
export UNSTRUCTURED_API_URL="https://<ORG_NAME>-<SECRET>.api.unstructuredapp.io/general/v0/general"

Basic usage will ingest a Markdown file to a single document. Here we demonstrate on LangChain’s readme:

import { UnstructuredLoader } from "@langchain/community/document_loaders/fs/unstructured";

const markdownPath = "../../../../README.md";

const loader = new UnstructuredLoader(markdownPath, {
  apiKey: process.env.UNSTRUCTURED_API_KEY,
  apiUrl: process.env.UNSTRUCTURED_API_URL,
});

const data = await loader.load();
console.log(data.slice(0, 5));

[
  Document {
    pageContent: '🦜️🔗 LangChain.js',
    metadata: {
      languages: [Array],
      filename: 'README.md',
      filetype: 'text/markdown',
      category: 'Title'
    }
  },
  Document {
    pageContent: '⚡ Building applications with LLMs through composability ⚡',
    metadata: {
      languages: [Array],
      filename: 'README.md',
      filetype: 'text/markdown',
      category: 'Title'
    }
  },
  Document {
    pageContent: 'Looking for the Python version? Check out LangChain.',
    metadata: {
      languages: [Array],
      parent_id: '7ea17bcb17b10f303cbb93b4cb95de93',
      filename: 'README.md',
      filetype: 'text/markdown',
      category: 'NarrativeText'
    }
  },
  Document {
    pageContent: 'To help you ship LangChain apps to production faster, check out LangSmith.\n' +
      'LangSmith is a unified developer platform for building, testing, and monitoring LLM applications.\n' +
      'Fill out this form to get on the waitlist or speak with our sales team.',
    metadata: {
      languages: [Array],
      parent_id: '7ea17bcb17b10f303cbb93b4cb95de93',
      filename: 'README.md',
      filetype: 'text/markdown',
      category: 'NarrativeText'
    }
  },
  Document {
    pageContent: '⚡️ Quick Install',
    metadata: {
      languages: [Array],
      filename: 'README.md',
      filetype: 'text/markdown',
      category: 'Title'
    }
  }
]

Retain Elements

Under the hood, Unstructured creates different “elements” for different chunks of text. By default we combine those together, but you can easily keep that separation by specifying chunkingStrategy: "by_title".

const loaderByTitle = new UnstructuredLoader(markdownPath, {
  chunkingStrategy: "by_title",
});

const loadedDocs = await loaderByTitle.load();

console.log(`Number of documents: ${loadedDocs.length}\n`);

for (const doc of loadedDocs.slice(0, 2)) {
  console.log(doc);
  console.log("\n");
}

Number of documents: 13

Document {
  pageContent: '🦜️🔗 LangChain.js\n' +
    '\n' +
    '⚡ Building applications with LLMs through composability ⚡\n' +
    '\n' +
    'Looking for the Python version? Check out LangChain.\n' +
    '\n' +
    'To help you ship LangChain apps to production faster, check out LangSmith.\n' +
    'LangSmith is a unified developer platform for building, testing, and monitoring LLM applications.\n' +
    'Fill out this form to get on the waitlist or speak with our sales team.',
  metadata: {
    filename: 'README.md',
    filetype: 'text/markdown',
    languages: [ 'eng' ],
    orig_elements: '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',
    category: 'CompositeElement'
  }
}


Document {
  pageContent: '⚡️ Quick Install\n' +
    '\n' +
    'You can use npm, yarn, or pnpm to install LangChain.js\n' +
    '\n' +
    'npm install -S langchain or yarn add langchain or pnpm add langchain\n' +
    '\n' +
    'typescript\n' +
    'import { ChatOpenAI } from "langchain/chat_models/openai";\n' +
    '\n' +
    '🌐 Supported Environments\n' +
    '\n' +
    'LangChain is written in TypeScript and can be used in:\n' +
    '\n' +
    'Node.js (ESM and CommonJS) - 18.x, 19.x, 20.x\n' +
    '\n' +
    'Cloudflare Workers\n' +
    '\n' +
    'Vercel / Next.js (Browser, Serverless and Edge functions)\n' +
    '\n' +
    'Supabase Edge Functions\n' +
    '\n' +
    'Browser\n' +
    '\n' +
    'Deno',
  metadata: {
    filename: 'README.md',
    filetype: 'text/markdown',
    languages: [ 'eng' ],
    orig_elements: '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',
    category: 'CompositeElement'
  }
}

Note that in this case we recover just one distinct element type:

const categories = new Set(data.map((document) => document.metadata.category));
console.log(categories);

Set(1) { 'CompositeElement' }