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# The Core Configuration Options

The options below control the MathJax Hub, and so determine the code behavior of MathJax. They are given with their default values.

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

  A comma-separated list of input and output jax to initialize at startup. Their main code is loaded only when they are actually used, so it is not inefficient to include jax that may not actually be used on the page. These are found in the `MathJax/jax` directory.

`extensions: []`

  A comma-separated list of extensions to load at startup. The default directory is `MathJax/extensions`. The `tex2jax` and `mml2jax` preprocessors can be listed here, as well as a number of TeX-specific extensions (see the TeX and LaTeX input section of the Getting Started document for more details). There is also a `FontWarnings` extension that you can use to inform your user that mathematics fonts are available that they can download to improve their experience of your site.

`config: []`

  A comma-separated list of configuration files to load when MathJax starts up, e.g., to define local macros, etc., and there is a sample config file named `config/local/local.js`. The default directory is the MathJax/config directory. The `MMLorHTML.js` configuration is the only other predefined configuration file.

`styleSheets: []`

  A comma-separated list of CSS stylesheet files to be loaded when MathJax starts up. The default directory is the MathJax/config directory.

`styles: {}`

  CSS selector: rules; styles to be defined dynamically at startup time.

`preJax: null and postJax: null`

  Patterns to remove from before and after math script tags. If you are not using one of the preprocessors, you need to insert something extra into your HTML file in order to avoid a bug in Internet Explorer. IE removes spaces from the DOM that it thinks are redundant, and since a `<script>` tag usually doesn’t add content to the page, if there is a space before and after a MathJax `<script>` tag, IE will remove the first space. When MathJax inserts the typeset mathematics, this means there will be no space before it and the preceding text. In order to avoid this, you should include some “guard characters” before or after the math SCRIPT tag; define the patterns you want to use below. Note that these are used as regular expressions, so you will need to quote special characters. Furthermore, since they are javascript strings, you must quote javascript special characters as well. So to obtain a backslash, you must use `\\` (doubled for javascript). For example, `"\\["` represents the pattern `\[` in the regular expression. That means that if you want an actual backslash in your guard characters, you need to use `"\\\\"` in order to get `\\` in the regular expression, and `\` in the actual text. If both preJax and postJax are defined, both must be present in order to be removed.

  See also the `preRemoveClass` comments below.

  Examples:

  > `preJax: "\\\\\\\\\"` makes a double backslash the preJax text

  > `preJax: "\\[\\[", postJax: "\\]\\]"` makes it so jax scripts must be enclosed in double brackets.

`preRemoveClass: "MathJax_Preview"`

  This is the CSS class name for math previews that will be removed preceding a MathJax SCRIPT tag. If the tag just before the MathJax `<script>` tag is of this class, its contents are removed when MathJax processes the `<script>` tag. This allows you to include a math preview in a form that will be displayed prior to MathJax performing its typesetting. It also avoids the Internet Explorer space-removal bug, and can be used in place of `preJax` and `postJax` if that is more convenient.

  For example

      <span class="MathJax_Preview">[math]</span><script  type="math/tex">...</script>

  would display “[math]” in place of the math until MathJax is able to typeset it.

  See also the `preJax` and `postJax` comments above.

`showProcessingMessages: true`

  This value controls whether the Processing Math: nn% messages are displayed in the lower left-hand corner. Set to `false` to prevent those messages (though file loading and other messages will still be shown).

`messageStyle: "normal"`

  This value controls the verbosity of the messages in the lower left-hand corner. Set it to `"none"` to eliminate all messages, or set it to `"simple"` to show “Loading...” and “Processing...” rather than showing the full file name or the percentage of the mathematics processed.

`displayAlign: "center" and displayIndent: "0em"`

  These two parameters control the alignment and shifting of displayed equations. The first can be `"left"`, `"center"`, or `"right"`, and determines the alignment of displayed equations. When the alignment is not `"center"`, the second determines an indentation from the left or right side for the displayed equations.

`delayStartupUntil: "none"`

  Normally MathJax will perform its startup commands (loading of configuration, styles, jax, and so on) as soon as it can. If you expect to be doing additional configuration on the page, however, you may want to have it wait until the page’s onload handler is called. If so, set this to `"onload"`. You can also set this to `"configured"`, in which case, MathJax will delay its startup until you explicitly call `MathJax.Hub.Configured()`. See Configuring MathJax after it is loaded for more details.

`skipStartupTypeset: false`

  Normally MathJax will typeset the mathematics on the page as soon as the page is loaded. If you want to delay that process, in which case you will need to call `MathJax.Hub.Typeset()` yourself by hand, set this value to `true`.

`elements: []`

  This is a list of DOM element ID’s that are the ones to process for mathematics when any of the Hub typesetting calls (Typeset, Process, Update, etc.) are called with no element specified, and during MathJax’s initial typesetting run when it starts up. This lets you restrict the processing to particular containers rather than scanning the entire document for mathematics. If none are supplied, the complete document is processed.

`menuSettings: { ... }`

  This block contains settings for the mathematics contextual menu that act as the defaults for the user’s settings in that menu. The possible values are:

  `zoom: "none"`

    This indicates when typeset mathematics should be zoomed. It can be set to `"None"`, `"Hover"`, `"Click"`, or `"Double-Click"` to set the zoom trigger.

  `CTRL: false, ALT: false, CMD: false, Shift: false`

    These values indicate which keys must be pressed in order for math zoom to be triggered. For example, if `CTRL` is set to `true` and `zoom` is `"Click"`, then math will be zoomed only when the user control-clicks on mathematics (i.e., clicks while holding down the CTRL key). If more than one is `true`, then all the indicated keys must be pressed for the zoom to occur.

  `zscale: "200%"`

    This is the zoom scaling factor, and it can be set to any of the values available in the Zoom Factor menu of the Settings submenu of the contextual menu.

  `context: "MathJax"`

    This controls what contextual menu will be presented when a right click (on a PC) or CTRL-click (on the Mac) occurs over a typeset equation. When set to `"MathJax"`, the MathJax contextual menu will appear; when set to `"Browser"`, the browser’s contextual menu will be used. For example, in Internet Explorer with the MathPlayer plugin, if this is set to `"Browser"`, you will get the MathPlayer contextual menu rather than the MathJax menu.

  There are also settings for `format`, `renderer`, and `font`, but these are maintained by MathJax and should not be set by the page author.

`errorSettings: { ... }`

  This block contains settings that control how MathJax responds to unexpected errors while processing mathematical equations. Rather than simply crash, MathJax can report an error and go on. The options you can set include:

  `message: ["[Math Processing Error]"]`

    This is an HTML snippet that will be inserted at the location of the mathematics for any formula that causes MathJax to produce an internal error (i.e., an error in the MathJax code itself). See the description of HTML snippets for details on how to represent HTML code in this way.

  `style: {color:"#CC0000", "font-style":"italic"}`

    This is the CSS style description to use for the error messages produced by internal MathJax errors. See the section on CSS style objects for details on how these are specified in JavaScript.

`v1.0-compatible: true`

  This controls whether MathJax issues the warning about not having an explicit configuration in the event that the jax array is empty after configuration is complete. If you really intend that array to be empty, set this flag to `false`. Note that setting this to false does not cause a default configuration file to be loaded.

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