jQuery is the more common of the two in our index: it runs on 32,999 websites against 7,674 for jQuery Migrate, and 7,674 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.
Query Migrate is a javascript library that allows you to preserve the compatibility of your jQuery code developed for versions of jQuery older than 1.9.
7,674 sites run both jQuery and jQuery Migrate. That is 100% of the sites using jQuery Migrate, 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.