KeTeX is faster, but supports a limited subset of LaTeX. MathJax supports essentially everything.
For most mathuses in blog posts KaTeX is going to provide a bettter user experience, but if you want to put a math paper on a webpageMathJax is the way to go.
Yes, it does. Supported extensions here [1]. Two more notable ones are mathtools and physics, both of which make writing latex on the web much more pleasant.
For most mathuses in blog posts KaTeX is going to provide a bettter user experience, but if you want to put a math paper on a webpageMathJax is the way to go.