KaTeX — Fast Math Typesetting for the Web

Introduction

KaTeX is a math typesetting library developed by Khan Academy that renders LaTeX expressions into HTML. It focuses on speed and correctness, producing the same high-quality output across all major browsers without relying on external services or image generation.

What KaTeX Does

• Renders LaTeX math expressions to HTML and MathML in the browser or on the server
• Produces output identical to LaTeX typesetting standards
• Supports hundreds of LaTeX functions including matrices, fractions, and symbols
• Provides an auto-render extension for processing all math on a page
• Works in Node.js for server-side rendering of math content

Architecture Overview

KaTeX parses LaTeX input into an abstract syntax tree, then walks the tree to build a virtual DOM of nested span elements. Each span is styled with precise CSS to replicate TeX layout rules. The library ships its own fonts (based on Computer Modern) and handles line breaking, sizing, and alignment internally.

Self-Hosting & Configuration

• Install via npm or load from a CDN with the accompanying CSS file
• Use katex.render() for targeted DOM rendering or katex.renderToString() for HTML strings
• Enable throwOnError: false to gracefully handle invalid LaTeX input
• Configure display mode, custom macros, and size limits via options
• Use the auto-render extension to batch-process all $$...$$ and (...) blocks on a page

Key Features

• Renders math synchronously with no layout reflow or flicker
• Produces accessible MathML output alongside visual HTML
• Supports copy-paste of rendered math as LaTeX source
• Works offline with self-hosted fonts and CSS
• Extensive macro and environment support including align, cases, and matrix

Comparison with Similar Tools

• MathJax — Supports more LaTeX commands and output formats but is larger and renders asynchronously
• Temml — Lighter MathML-only renderer; KaTeX provides both HTML and MathML output
• LaTeX.js — Full LaTeX document parser; KaTeX focuses on math expressions only
• MathLive — Interactive math editor; KaTeX is a display-only renderer

FAQ

Q: What LaTeX commands does KaTeX support? A: KaTeX supports most common LaTeX math commands. The full list is in the documentation under "Supported Functions."

Q: Can KaTeX render server-side? A: Yes. Use katex.renderToString() in Node.js to produce HTML strings for SSR.

Q: How does performance compare to MathJax? A: KaTeX is significantly faster because it renders synchronously in a single pass, while MathJax uses multiple asynchronous layout passes.

Q: Does it work with React? A: Yes. Libraries like react-katex wrap KaTeX for use as React components, or you can call renderToString directly.

Sources

• https://github.com/KaTeX/KaTeX
• https://katex.org