# Configuring MathJax

The various components of MathJax, including its input and output processors, its extensions, and the MathJax core, all can be configured though a `MathJax` global object that specifies the configuration you want to use. The `MathJax` object consists of sub-objects that configure the individual components of MathJax. For example, the input/tex component is configured through a `tex` block within the `MathJax` object, while the startup component is configured through the `startup` block.

These blocks are JavaScript objects that includes `name: value` pairs giving the names of parameters and their values, with pairs separated by commas. Be careful not to include a comma after the last value, however, as some browsers will fail to process the configuration if you do.

Some blocks may contain further sub-blocks. For example, the `tex` block can have a `macros` sub-block that pre-defines macros, and a `tagformat` block (when the tagformat component is used) to define how equation tags are displayed and handled.

For example,

    window.MathJax = {
      loader: {
        load: ['[tex]/tagformat']
      },
      startup: {
        pageReady: () => {
          alert('Running MathJax');
          return MathJax.startup.defaultPageReady();
        }
      },
      tex: {
        packages: {'[+]': ['tagformat']},
        tagSide: 'left',
        macros: {
          RR: '{\\bf R}',
          bold: ['{\\bf #1}',1]
        },
        tagformat: {
           tag: (n) => '[' + n + ']'
        }
      }
    };

is a configuration that asks for the tagformat extension to be loaded, sets up the startup component to have a function that it runs when the page (and MathJax) are ready (the function issues an alert and then does the usual `pageReady()` function, which typesets the page), configures the TeX input component to use the tagformat extension, asks for displayed equations to be typeset to the left (rather than centered), defines two macros, and finally set the tagging so that it uses square brackets rather than parentheses for equation numbers and tags.

Note the special notation used with the `packages` option above. The `packages` property is an array of extension names, but the configuration uses a special object to add to that array rather than replace it. If the option you are setting is an array, and you provide an object that has a single properly whose name is `'[+]'` and whose value is an array, then that array will be appended to the default value for the option you are setting. So in the example above, the `'tagformat'` string is added to the default `packages` array (without your needing to know what that default value is).

Similarly, if you use an object with a single property whose name is `'[-]'` and whose value is an array, the elements in that array are removed from the default value of the option you are setting. For example,

    packages: {'[-]': ['autoload', 'require']}

would remove the autoload and require packages from the default `packages` array.

Finally, you can combine `'[+]'` and `'[-]'` in one object to do both actions. E.g.,

    packages: {'[+]': ['enclose'], '[-]': ['autoload', 'require']}

would remove the autoload and require packages from the default `packages` array, and add enclose to the result.

In the links below, the various options are first listed with their default values as a complete configuration block, and then each option is explained further below that.

More Information

- Input Processor Options
  - TeX Input Processor Options
  - MathML Input Processor Options
  - AsciiMath Input Processor Options
- Output Processor Options
  - CommonHTML Output Processor Options
  - SVG Output Processor Options
- Document Options
- Accessibility Extensions Options
- Contextual Menu Options
- Safe Extension Options
- Startup and Loader Options
  - Loader Options
  - Startup Options