Streamdown

A drop-in replacement for react-markdown, designed for AI-powered streaming.

Overview

Formatting Markdown is easy, but when you tokenize and stream it, new challenges arise. Streamdown is built specifically to handle the unique requirements of streaming Markdown content from AI models, providing seamless formatting even with incomplete or unterminated Markdown blocks.

Streamdown powers the AI Elements Message component but can be installed as a standalone package for your own streaming needs.

Features

🚀 Drop-in replacement for react-markdown
🔄 Streaming-optimized - Handles incomplete Markdown gracefully
🎨 Unterminated block parsing - Styles incomplete bold, italic, code, links, and headings
📊 GitHub Flavored Markdown - Tables, task lists, and strikethrough support
🔢 Math rendering - LaTeX equations via KaTeX
📈 Mermaid diagrams - Render Mermaid diagrams as code blocks with a button to render them
🎯 Code syntax highlighting - Beautiful code blocks with Shiki
🛡️ Security-first - Built with rehype-harden for safe rendering
⚡ Performance optimized - Memoized rendering for efficient updates

Installation

npm i streamdown

Then, update your Tailwind globals.css to include the following.

@source "../node_modules/streamdown/dist/index.js";

Make sure the path matches the location of the node_modules folder in your project. This will ensure that the Streamdown styles are applied to your project.

Usage

You can use Streamdown in your React application like this:

import { Streamdown } from "streamdown";

export default function Page() {
  const markdown = "# Hello World\n\nThis is **streaming** markdown!";

  return <Streamdown>{markdown}</Streamdown>;
}

For more info, see the documentation.

Browser Support

Streamdown requires browsers that support RegExp lookbehind assertions. This means:

Safari 16.5+ (iOS 16.5+, macOS Ventura 13.4+)
Chrome 62+
Edge 79+
Firefox 78+

The lookbehind assertion requirement comes from dependencies (particularly Shiki for syntax highlighting and mdast-util-gfm-autolink-literal). Older browsers will crash when attempting to parse these regular expressions.

If you need to support older browsers, particularly iOS Safari < 16.5, you may need to implement conditional loading or provide a fallback rendering solution.