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# MathJax Output Formats

Currently, MathJax can render math in three ways:

- Using HTML-with-CSS to lay out the mathematics,
- Using SVG to lay out the mathematics, or
- Using a browser’s native MathML support.

These are implemented by the HTML-CSS, SVG and NativeMML output processors.

If you are using one of the combined configuration files, then this will select one of these output processors for you. If the config file ends in `_HTML`, then it is the HTML-CSS output processor, and if it ends in `_SVG` then the SVG output processor will be used. If it ends in `_HTMLorMML`, then the NativeMML output processor will be chosen if the browser supports it well enough, otherwise HTML-CSS output will be used.

If you are performing your own in-line or file-based configuration, you select which one you want to use by including either `"output/HTML-CSS"`, `"output/SVG"`, or `"output/NativeMML"` in the jax array of your MathJax configuration. For example

    jax: ["input/TeX","output/HTML-CSS"]

would specify TeX input and HTML-with-CSS output for the mathematics in your document.

The HTML-CSS output processor produces high-quality output in all major browsers, with results that are consistent across browsers and operating systems. This is MathJax’s primary output mode. Its major advantage is its quality and consistency; its drawback is that it is slower than the NativeMML mode at rendering the mathematics. Historically, the performance in Internet Explorer (and IE8 in particular) was quite poor, with the page getting slower and slower as more math is processed. MathJax version 2.0 includes a number of optimizations to improve the display performance in IE, and it is now more comparable to other browsers. The HTML-CSS output uses web-based fonts so that users don’t have to have math fonts installed on their computers, which introduces some printing issues in certain browsers.

The SVG output processor is new in MathJax version 2.0, and it uses Scalable Vector Graphics to render the mathematics on the page. SVG is supported in all the major browsers and most mobile devices; note, however, that Internet Explorer prior to IE9 does not support SVG, and IE9 only does in “IE9 standards mode”, not its emulation modes for earlier versions. The SVG output mode is high quality and slightly faster than HTML-CSS, and it does not suffer from some of the font-related issues that HTML-CSS does, so prints well in all browsers. This format also works well in some ebook readers (e.g., iBooks). The disadvantages of this mode are the following: first, Internet Explorer only supports SVG in IE9 and later versions (and then only in IE9 standards mode or above), and some versions of the Android Internet browser don’t have SVG enabled. Second, it does not take advantage of STIX fonts, and so only has access to the characters in the web-based fonts, and third, its variable-width tables become fixed size once they are typeset, and don’t rescale if the window size changes (for example). Since equation numbers are handled through variable-width tables, that means equation numbers may not stay at the edge of the window if it is resized. For these reasons it is probably best not to force the use of SVG output unless you have some control over the browsers that are used to view your documents.

The NativeMML output processor uses the browser’s internal MathML support (if any) to render the mathematics. Currently, Firefox has native support for MathML, and IE has the MathPlayer plugin for rendering MathML. Opera has some built-in support for MathML that works well with simple equations, but fails with more complex formulas, so we don’t recommend using the NativeMML output processor with Opera. Safari has some support for MathML since version 5.1, but the quality is not as high as either Firefox’s implementation or IE with MathPlayer. Chrome, Konqueror, and most other browsers don’t support MathML natively, but this may change in the future, since MathML is part of the HTML5 specification.

The advantage of the NativeMML output Processor is its speed, since native MathML support is much faster than using complicated HTML and CSS to typeset mathematics, as the HTML-CSS output processor does. The disadvantage is that you are dependent on the browser’s MathML implementation for your rendering, and these vary in quality of output and completeness of implementation. MathJax relies on features that are not available in some renderers (for example, Firefox’s MathML support does not implement the features needed for labeled equations). The results using the NativeMML output processor may have spacing or other rendering problems that are outside of MathJax’s control.

## Automatic Selection of the Output Processor

Since not all browsers support MathML natively, it would be unwise to choose the NativeMML output processor unless you are sure of your audience’s browser capabilities. MathJax can help with that, however, since a number of its combined configuration files will select NativeMML output when the browser supports it well enough, and HTML-CSS output otherwise. These are the configuration files that end in `_HTMLorMML`.

If you are doing your own configuration, there is a special configuration file that you can include that will choose between NativeMML and HTML-CSS depending on the browser in use. To invoke it, add `"MMLorHTML.js"` to your configuration’s config array, and do not include an output processor in your jax array; MathJax will fill that in for you based on the abilities of your user’s browser.

    config: ["MMLorHTML.js"],
    jax: ["input/TeX"]

By default, MathJax will choose HTML-CSS in all browsers except for one case: Internet Explorer when the MathPlayer plugin is present. In the past, MathJax selected NativeMML output for Firefox as well, but we have found that there are too many rendering issues with Firefox’s native MathML implementation, and so MathJax now selects HTML-CSS output for Firefox by default as well. Users can still use the Mathjax contextual menu to select the NativeMML renderer if they wish to choose greater speed at the expense of some quality.

You can customize which choice MathJax makes on a browser-by-browser basis or a global basis. See the `config/default.js` file or the Configuring MMLorHTML section for further details. As an example, this configuration tells MathJax to use native MathML support rather than HTML-CSS output for Firefox:

    <script type="text/x-mathjax-config">
      MathJax.Hub.Config({
        MMLorHTML: { prefer: { Firefox: "MML" } }
      });
    </script>
    <script type="text/javascript"
      src="http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML">
    </script>

With this configuration, MathML output will be used for both Firefox and IE with the MathPlayer plugin. Note, however, that a user can employ the MathJax contextual menu to select the other renderer if he or she wishes.

MathJax produces MathML that models the underlying mathematics as best it can, rather than using complicated hacks to improve output for a particular MathML implementation. When you make the choice to use the NativeMML output processor, you are making a trade-off: gaining speed at the expense of quality and reliability, a decision that should not be taken lightly.

## Automatic Line Breaking

The HTML-CSS and SVG output processors implement (most of) the MathML3 automatic line-breaking specification. (The NativeMML output processor relies on the browser’s native MathML support to handle line breaking when it is used.) Since line-breaking takes extra processing and so can slow down the mathematical output, it is off by default, but you can enable it by adding

    <script type="text/x-mathjax-config">
    MathJax.Hub.Config({
      "HTML-CSS": { linebreaks: { automatic: true } },
             SVG: { linebreaks: { automatic: true } }
    });
    </script>

to your page just before the `<script>` tag that loads `MathJax.js` itself.

Note that line breaking only applies to displayed equations, not in-line equations (unless the in-line euqation is itself longer than a line), and that the line-breaks are only computed once when the equation is initially typeset, and do not change if the user changes the window size, or if the container changes size for some other reason.

You can control what width is used to determine where the line breaks shoud occur using the `container` parameter of the `linebreaks` block. By default it is the width of the containing element, but you can make it a fixed width, or make it a percentage of the container. See the HTML-CSS configuration or SVG configuration pages for more details.

The linbe-breaking algorithm uses the nesting depth, the type of operator, the size of spaces, and other factors to decide on the breakpoints, but it does not know the meaning of the mathematics, and may not choose the optimal breakpoints. We will continue to work on the algorithm as we gain information from its actual use in the field. If you are using MathML as your input format, you can use the `linebreak="goodbreak"` and `linebreak="badbreak"` attributes on `<mo>` elements to help MathJax pick the best breakpoints for your mathematics.

## HTML-CSS with IE

The performance of MathJax in Internet Explorer 8 and 9 has been substantially improved in version 2.0. The HTML-CSS output processing was redesigned to avoid the page reflows that were the main source of the speed problem in I8 and IE9. For test pages having between 20 and 50 typeset expressions, we see an 80% reduction in output processing time for IE8, a 50% reduction for IE9, and between 15% and 25% reduction for most other browsers over the v1.1a times. Since the processing time in v1.1a grows non-linearly in IE, you should see even larger savings for pages with more equations when using v2.0.

In the past, we recommended forcing IE8 and IE9 into IE7-emulation mode in order to get better performance. That is no longer necessary. Indeed, the fastest modes in IE8 and IE9 now are their IE8 standards and IE9 standards modes, so it is best to force the highest mode possible. That can be accomplished by adding

    <meta http-equiv="X-UA-Compatible" content="IE=edge">

at the top of the `<head>` section of your HTML documents. Note that this line must come at the beginning of the `<head>`, before any stylesheets, scripts, or other content are loaded.

## HTML-CSS Extensions

The HTML-CSS output jax uses elements with width set to 100% when it typesets displayed equations. If there are floating elements on the left or right, this can mean that displayed mathematics isn’t properly centered, and can cause equation numbers to overlap the floating content. To avoid this, you can specify the handle-floats extension in the extensions array of your HTML-CSS configuration block.

    "HTML-CSS": {
      extensions: ["handle-floats.js"]
    }

This will use CSS that puts the displayed equations into elements that work like tabel cells, and won’t overlap the floaring content. Because this is somewhat of a misuse of CSS, it is not used by default, but it has proved successful in most situations, so you may consider using it in pages that include material that floats to the left or right of text containing displayed mathematics, especially when equation numbers or tags are used.

See the HTML-CSS configuration options for other options of the HTML-CSS output jax.

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