# 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.

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`

or
`\begin{enumerate}...\end{enumerate}`

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.

There are two exception to this rule. First, MathJax supports the
`\ref`

macro outside of math-mode. Second, MathJax supports some
macros that add text within math-mode (such as `\text{}`

) as well as
`$...$`

and `\(...\)`

to switch back into math-mode, along with
`\$`

to escape a dollar sign. MathJax does not perform other macros
inside these text blocks, however, in general. So, for example,
`\text{some \textbf{bold} text}`

will produce the output “some
\textbf{bold} text”, not “some **bold** text”.

There is an extension (new in version 3.1) that implements a number
of text-mode macros within the `\text{}`

macro and other ones that
produce text-mode material. See the textmacros
documentation for details.

Second, some features in MathJax might be necessarily limited. For
example, MathJax only implements a limited subset of the `array`

environment’s preamble; i.e., only the `l`

, `r`

, `c`

, and `|`

characters alongside `:`

for dashed lines — everything else is
ignored.