Differences from Actual TeX

.. _tex-differences:

########################### Differences from Actual TeX ###########################

Since MathJax renders for the web, and TeX is a print layout engine, there are natural limitations to which parts of TeX can be supported in a reasonable way. Accordingly, there are several differences between "real" TeX/LaTeX systems and MathJax's TeX input jax.

First and foremost, the TeX input processor implements only the math-mode macros of TeX and LaTeX, not the text-mode macros. MathJax expects that you will use standard HTML tags to handle formatting the text of your page; MathJax only handles the mathematics. So, for example, MathJax does not implement \emph, \begin{enumerate}...\end{enumerate}, \begin{tabular}...\end{tabular} or other text-mode macros or environments. You must use HTML to handle such formatting tasks. If you need a LaTeX-to-HTML converter, you should consider other options <https://www.google.com/search?q=latex+to+html+converter>_.

There are a few exception to this rule. First, MathJax supports the \ref and \eqref macros outside of math mode. Also, MathJax supports some macros that add text within math mode (such as the \text{} macro), and allows $...$ and \(...\) to switch back into math mode from within text mode. In v3 and below, MathJax did not process macros within text mode, other than escaping special characters like \$, \{, and \}. So, for example, \text{some \textbf{bold} text} would produce the output "some \textbf{bold} text", not "some bold text" in v3.

Version 3.1 introduced a new [tex]/textmacros extension that implemented a number of text-mode macros within \text{} and other macros that produce text-mode material. See the :ref:tex-textmacros documentation for details. In version 4, this extension is included by default in all the combined configuration files, so \text{some \textbf{bold} text} does produce "some bold text" in v4.

Second, because MathJax concentrates in math-mode, not text-mode, some macros that initiate text-mode in actual TeX may stay in math-mode in MathJax. For example, the argument \llap{} and \rlap{} in actual TeX is typeset in text-mode, but in MathJax, these remain in math-mode so that you don't have to use dollar signs to go back into math-mode as you would in actual TeX.

Third, TeX's rules about how arguments to macros are subtle and not always consistent. For example, \sqrt \frac a b will produce the square root of the fraction a/b, but \hat \frac a b will produce an error. Both of these expressions represent poor practice, as the arguments should be within braces to make the grouping clear: \sqrt{\frac{a}{b}} and \hat{\frac{a}{b}}. MathJax standardizes the handling of braces more than TeX does, and sometimes requires the braces when TeX may not. So some expression that TeX or LaTeX will accept will cause errors in MathJax if they don't include the usual braces.

Finally, some features in MathJax might be more limited than in actual LaTeX. For example, MathJax doesn't implement the \multicolumn, \multirow, \omit, \intertext, or \vadjust macros, so table layout is more restricted in MathJax, currently. Similarly, \hfil and related macros are only allowed at the left and right-hand ends of the contents of a cell within a table.

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