There are several of these. base65536 is the one that seems to pop up the most often on HN, although base2048 is more useful for Twitter. On the GitHub page the

There are several of these. base65536 is the one that seems to pop up the most often on HN, although base2048 is more useful for Twitter. On the GitHub page the dev helpfully links to the various implementations: https://github.com/qntm/base2048 https://github.com/qntm/base2048