MathJax 2 vs 3 vs 4: Differences Explained with Live Examples

MathJax 3 is a complete rewrite of MathJax 2, and MathJax 4 builds on version 3 with new fonts and line breaking. This page compares all three versions in one table, then shows the differences you can see for yourself in the live preview.

Open the MathJax 2, 3 and 4 live preview →

Quick comparison

Feature	MathJax 2	MathJax 3	MathJax 4
Status	Legacy, no longer developed	Stable (3.2.2)	Current
Configuration	`MathJax.Hub.Config()` in a `text/x-mathjax-config` script	`window.MathJax` object	Same as 3
Re-render after page load	`MathJax.Hub.Queue(["Typeset", MathJax.Hub])`	`MathJax.typesetPromise()`	Same as 3
CDN file	`mathjax@2.7.9/MathJax.js?config=…`	`mathjax@3/es5/tex-chtml.js`	`mathjax@4/tex-chtml.js`
Output formats	HTML-CSS, CommonHTML, SVG, NativeMML	CommonHTML, SVG	CommonHTML, SVG
Default font	MathJax TeX	MathJax TeX	New Computer Modern (`mathjax-newcm`)
Automatic line breaking	Optional, off by default	Not supported	On for inline math; display math needs `displayOverflow: 'linebreak'`
`\color{red}{x} + y`	Colours only `x`	Colours `x + y` (works like LaTeX)	Same as 3
mhchem chemistry	Older version; `\pu` doesn't work by default	Current version, loads automatically on `\ce` or `\pu`	Same as 3
$...$ inline math	Off by default	Off by default	Off by default
`\$` for a literal dollar sign	Off by default (`processEscapes`)	On by default	On by default
AsciiMath	Included in `TeX-MML-AM_*` configs	Must be loaded separately	Must be loaded separately
Ignore class	`tex2jax_ignore`	`mathjax_ignore`	`mathjax_ignore`

MathJax 2 vs MathJax 3

This is the big jump. MathJax 3 was rewritten in TypeScript and renders much faster than MathJax 2, but almost everything you write to set it up changes:

The script URL and the configuration format are different.
The MathJax.Hub API is gone, so code that re-renders math needs updating.
HTML-CSS and NativeMML output were removed; CommonHTML and SVG remain.
Automatic line breaking was dropped, so long equations overflow instead of wrapping.
\color now behaves like real LaTeX, which can recolour more than you expect.

The MathJax 2 to 3 migration guide covers each change with before-and-after code.

MathJax 3 vs MathJax 4

MathJax 4 keeps the version 3 configuration and API, so most sites can upgrade by changing the script URL. The visible differences are:

Fonts: the new default font covers many more characters, and glyph shapes and spacing look slightly different.
Line breaking: long inline math wraps at top-level operators such as + and =, but not inside brackets like (a + b + c)^2.
File paths: there is no es5/ folder in the CDN URL.
Accessibility: speech and keyboard exploration of equations are improved.

See the differences live

Each link opens an example in the live preview, rendered in MathJax 2, 3 and 4 side by side:

Long equation: MathJax 2 and 3 overflow, while MathJax 4 wraps the inline sum.
Chemistry (mhchem): \pu{123 kJ/mol} fails in MathJax 2 but works in 3 and 4.
Calculus: compare fonts and spacing across all three versions.

Which version should you use?

New site: use MathJax 4.
Already on MathJax 3: upgrading to 4 is usually a URL change. Check that the new font and line breaking look right for your content.
Still on MathJax 2: plan a migration. MathJax 2 still works, but it is no longer developed and is slower than 3 and 4.

Test your own content

The quickest way to find out what changes for your site is to paste real content into the MathJax live preview and compare MathJax 2.7.9, 3.2.2 and 4.1.3 side by side.

Compare your content in MathJax 2, 3 and 4 →