# TeX and LaTeX extensions

While MathJax includes nearly all of the Plain TeX math macros, and many of the LaTeX macros and environments, not everything is implemented in the core TeX input processor. Some less-used commands are defined in extensions to the TeX processor. MathJax will load some extensions automatically when you first use the commands they implement (for example, the `\color` macro is implemented in the `color` extension, but MathJax loads this extension itself when you use that macro). While most extensions are set up to load automatically, there are a few that you would need to load explicitly yourself. See the autoload extension below for how to configure which extensions to autoload.

## Loading TeX Extensions

To enable one of the TeX extensions you need to do two things: load the extension, and configure TeX to include it in its package setup. For the first, to load an extension as a component, add its name to the `load` array in the `loader` block of your MathJax configuration. For example, to load the `color` extension, add `'[tex]/color'` to the load array, as in the example below. To do the second, add the extension name to `packages` array in the `tex` block of your configuration. You can use the special `'[+]'` notation to append it to the default packages (so you don’t need to know what they are). For example:

    window.MathJax = {
      loader: {load: ['[tex]/color']},
      tex: {packages: {'[+]': ['color']}}
    };

will load the `color` extension and configure the TeX input jax to enable it.

A number of extensions are already loaded and configured in the components that contain the TeX extension. The `input/tex`, and the combined components containing `tex` and not ending in `-full` include the `ams`, `newcommand`, `noundefined`, `require`, `autoload`, and `configmacros` extensions, with the other extensions being autoloaded as needed. The `input/tex-base` component has no extensions loaded, while the `input/tex-full` and the combined extensions ending in `-full` load all the extensions.

If you load a component that has an extension you don’t want to use, you can disable it by removing it from the `package` array in the `tex` block of your MathJax configuration. For example, to disable `\require` and autoloading of extensions, use

    window.MathJax = {
      tex: {packages: {'[-]': ['require', 'autoload']}}
    };

if you are using, for example, the `tex-chtml.js` combined component file.

## Loading Extensions at Run Time

You can also load these extensions from within a math expression using the non-standard `\require{extension}` macro. For example

    \(\require{color}\)

would load the color extension into the page. This way you you can load extensions into pages that didn’t load them in their configurations (and prevents you from having to load all the extensions into all pages even if they aren’t used).

## Configuring TeX Extensions

Some extensions have options that control their behavior. For example, the color extension allows you to set the padding and border-width used for the `\colorbox` and `\fcolorbox` macros. Such extensions are configured using a block within the `tex` configuration of your MathJax configuration object. The block has the same name as the extension, and contains the options you want to set for that extension. For example,

    window.MathJax = {
      loader: {load: ['[tex]/color']},
      tex: {
        packages: {'[+]': ['color']},
        color: {
          padding: '5px'
        }
      }
    };

would set the padding for `\colorbox` to be 5 pixels.

See the Configuring MathJax section for details about how to configure MathJax in general, and TeX Extension Options for the options for individual extensions.

For extensions that are not loaded explicitly but may be loaded via the autoload package or the `\require` macro, you can’t include the configuration within the `tex` block, because MathJax will not know the options that are available (since the extension hasn’t been loaded yet). In that case, move the configuration block to the top level of the MathJax configuration object and prefix it with `[tex]/`, as in:

    window.MathJax = {
      '[tex]/color': {
        padding: '5px'
      }
    };