As of version 2.2, MathJax’s user interface (including its contextual menu, its help and about dialog boxes, and its warning messages) can all be localized to appear in languages other than English. Currently, there are translations into French and German, but we hope that other languages will follow soon. Users who wish to help in the translation process should contact the MathJax team via the MathJax development forum. A quick guide to translating MathJax is available in the Development wiki.
The language used by MathJax can be selected using the MathJax contextual menu. It includes a Language submenu that lists the available languages; selecting one will change the MathJax user interface to use that language.
Page authors can select a default language for MathJax so that, for example, a page that is written in French will have MathJax’s user interface also in French. To do this, add &locale=XX after the configuration file in the <script> tag that loads the MathJax.js file, where XX is the two-letter code for the language. Currently the choices are en, fr, and de. For example:
will load MathJax using the French language. Users can still override this setting using the Language submenu of the MathJax contextual menu. This submenu can be disabled, however, using the MathMenu configuration options.