jQuery is the more common of the two in our index: it runs on 29,967 websites against 14 for SimplexNoise.js, and 13 sites use both. Counts come from real scans, not vendor claims.
jQuery is a JavaScript library which is a free, open-source software designed to simplify HTML DOM tree traversal and manipulation, as well as event handling, CSS animation, and Ajax.
SimplexNoise.js is a library that generates pseudorandom noise functions, designed for use in video games, graphical applications, and demoscene production.
13 sites run both jQuery and SimplexNoise.js. That is 93% of the sites using SimplexNoise.js, the smaller of the two.
Want to know which one a particular site uses? Look it up and see its whole stack, or compare two sites side by side.