the reason why I prefer to use a cdn is because it is a games theory example come to life here - if everyone used the cdn version then any user coming to your site would most likely have the cdn version in their cache and thus performance would go up, but if you use the cdn version and your competitors don&#x27;t their performance is slightly better than yours and so on and so forth. Games theory indicates that in most games of this sort cooperation is better than non-cooperation.<p>And really if you are using one of the major libraries and a major CDN (Google, JQuery, etc.) over time your users will end up having the stuff in the cache, either from you or from others having used the same library version and cdn.<p>I suppose someone has done a study on CDN spreading of libraries and CDNS among users, so that you could figure out what the chance is that a user coming to your site will have a specific library cached - there&#x27;s this <a href="http:&#x2F;&#x2F;www.stevesouders.com&#x2F;blog&#x2F;2013&#x2F;03&#x2F;18&#x2F;http-archive-jquery&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.stevesouders.com&#x2F;blog&#x2F;2013&#x2F;03&#x2F;18&#x2F;http-archive-jqu...</a> but it is 3 years ago, really this information would need to be maintained at least annually to tell you what your top cdn would be for a library.