# AsciiMath Support

The support for AsciiMath in MathJax involves two functions: the first looks for mathematics within your web page (indicated by delimiters like ``...``) and marks the mathematics for later processing by MathJax, and the second is what converts the AsciiMath notation into MathJax’s internal format, where one of MathJax’s output processors then displays it in the web page. In MathJax version 2, these were separated into distinct components (the `asciimath2jax` preprocessor and the AsciiMath input jax), but in version 3, the `asciimath2jax` functions have been folded into the AsciiMath input jax.

The AsciiMath input jax actually includes a copy of `ASCIIMathML.js` itself (see the AsciiMath home page for details). This means that the results of MathJax’s AsciiMath processing should be the same as using the actual `ASCIIMathML.js` package (at least as far as the MathML that it generates is concerned). Thanks go to David Lippman for writing the initial version of the AsciiMath preprocessor and input jax and for the ongoing improvements from the AsciiMath community.

The AsciiMath input jax handles only the original ASCIIMathML notation (from ASCIIMathML v1.4.7), not the extended LaTeXMathML notation added in version 2.0 of ASCIIMathML, though the AsciiMath input jax does expose the tables that define the symbols that AsciiMath processes, and so it would be possible to extend them to include additional symbols. In general, it is probably better to use MathJax’s TeX input jax to handle LaTeX notation.

AsciiMath can be configured to look for whatever markers you want to use for your math delimiters. See the AsciiMath configuration options section for details on how to customize the action of the AsciiMath input jax.

## Loading the AsciiMath Component

The AsciiMath input jax has not yet been fully ported to version 3. Instead, the AsciiMath component uses the version 2 AsciiMath input jax together with some of the legacy version 2 code patched into the version 3 framework. This is less efficient, and somewhat larger, than a pure version-3 solution would be, and it can complicate the configuration process. A full version-3 port of AsciiMath is planned for a future release.

Because AsciiMath hasn’t been fully ported to version 3, none of the combined components include it. So in order to use AsciiMath notation, you will need to configure MathJax to load it yourself by adding `input/asciimath` to the `load` array in the `loader` block of your MathJax configuration. For example,

    <script>
    MathJax = {
      loader: {load: ['input/asciimath', 'output/chtml', 'ui/menu']},
    };
    </script>
    <script type="text/javascript" id="MathJax-script" async
      src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/startup.js">
    </script>

would load the AsciiMath input jax, the CommonHTML output jax, and the contextual menu component.

## AsciiMath delimiters

By default, the AsciiMath processor defines the back-tick (```) as the delimiters for mathematics in AsciiMath format. It does not define `$...$` as math delimiters. That is because dollar signs appear too often in non-mathematical settings, which could cause some text to be treated as mathematics unexpectedly. For example, with single-dollar delimiters, “… the cost is $2.50 for the first one, and $2.00 for each additional one …” would cause the phrase “2.50 for the first one, and” to be treated as mathematics since it falls between dollar signs. For this reason, if you want to use single-dollars for AsciiMath notation, you must enable that explicitly in your configuration:

    window.MathJax = {
      loader: {
        load: ['input/asciimath']
      },
      asciimath: {
        delimiters: [['$','$'], ['`','`']]
      }
    });

Note that the dollar signs are frequently used as a delimiter for mathematics in the TeX format, and you can not enable the dollar-sign delimiter for both. It is probably best to leave dollar signs for TeX notation.

See the AsciiMath Input Processor Options page, for additional configuration parameters that you can specify for the AsciiMath input processor.

## AsciiMath in HTML documents

The AsciiMath syntax is described on the official AsciiMath homepage.

Keep in mind that your mathematics is part of an HTML document, so you need to be aware of the special characters used by HTML as part of its markup. There cannot be HTML tags within the math delimiters (other than `<br>`, `<wbr>`, and HTML comments) as AsciiMath-formatted math does not include HTML tags. Also, since the mathematics is initially given as text in the page, you need to be careful that your mathematics doesn’t look like HTML tags to the browser, which parses the page before MathJax gets to see it. In particular, that means that you have to be careful about things like less-than and greater-than signs (`<` and `>`), and ampersands (`&`), which have special meaning to web browsers. For example,

    ... when `x<y` we have ...

will cause a problem, because the browser will think `<y` is the beginning of a tag named `y` (even though there is no such tag in HTML). When this happens, the browser will think the tag continues up to the next `>` in the document (typically the end of the next actual tag in the HTML file), and you may notice that you are missing part of the text of the document. In the example above, the “`<y`” and “`we have ...`” will not be displayed because the browser thinks it is part of the tag starting at `<y`. This is one indication you can use to spot this problem; it is a common error and should be avoided.

Usually, it is sufficient simply to put spaces around these symbols to cause the browser to avoid them, so

    ... when `x < y` we have ...

should work. Alternatively, you can use the HTML entities `&lt;`, `&gt;` and `&amp;` to encode these characters so that the browser will not interpret them, but MathJax will. E.g.,

    ... when `x &lt; y` we have ...

Keep in mind that the browser interprets your text before MathJax does.