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# The mml2jax Preprocessor

The options below control the operation of the mml2jax preprocessor that is run when you include `"mml2jax.js"` in the extensions array of your configuration. They are listed with their default values. To set any of these options, include a `mml2jax` section in your `MathJax.Hub.Config()` call. For example

    MathJax.Hub.Config({
      mml2jax: {
        preview: "none"
      }
    });

would set the `preview` parameter to `"none"`.

`preview: "alttext"`

  This controls whether mml2jax inserts `MathJax_Preview` spans to make a preview available, and what preview to use, when it locates mathematics on the page. The default is `"alttext"`, which means use the `<math>` tag’s `alttext` attribute as the preview (visible until it is processed by MathJax), if the tag has one. Set it to `"none"` to prevent the previews from being inserted (the math will simply disappear until it is typeset). Set it to an array containing the description of an HTML snippet in order to use the same preview for all equations on the page.

  Examples:

      preview: ["[math]"],     //  insert the text "[math]" as the preview

      preview: [["img",{src: "/images/mypic.jpg"}]],  // insert an image as the preview

  See the description of HTML snippets for details on how to represent HTML code in this way.

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