We are currently in beta release for v3.0, with an official release being prepared.

Please follow the Technical Committee work on the MathJax Developer mailing list as well as the repository at https://github.com/mathjax/mathjax-v3.

Examples are available in the MathJax3 demos repository for how to use MathJax 3 in a browser setting, and MathJax3 node demos repository for examples of how to use MathJax3 in node applications.