MathJax's TEX input jax implements: Nearly all plain TEX math-mode macros But not stretchable glue or rules, no low-level box commands, and no \halign Some standard LATEX macros and environments (\frac, \sqrt[]{}, \mathbb, etc.) AMS symbols and AMS math environments (gather, split, align, etc.) Some extensions (e.g., \unicode) The complete list of macros supported by MathJax