[occamrazor]

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.

[singhrac]

I think MathJax has really caught up in speed in the past few (5) years with MathJax 3. I would pick MathJax today for compatibility reasons.

[tombert]

Interesting; does MathJax support the AMS extensions? That was my issue with KaTeX in the past.

[abdullahkhalids]

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.

[1] https://docs.mathjax.org/en/latest/input/tex/extensions/inde...