> Another alternative would be to encode the content of a MathB.in post and embed it into the URL, which could then be distributed with others. Upon visiting the URL, the application would read the encoded content from the URL, decode it, and render it.

I made something like this a couple of years ago; it was only 60-something lines long. Very simple and a bit of fun to play with: https://github.com/ea935/maths