When I was learning to be a web developer it was beaten into my head that if you were building a site and loading 3rd party scripts on it (e.g. jQuery, Bootstrap), you should load them from a CDN because if a user on your site had been to another site that used jQuery (likely) and they used the same version of jQuery (somewhat likely), and that other site also used the same CDN for jQuery (i.e. `https://code.jquery.com/`, which was pretty likely given we didn’t have as many widely available CDNs back then), then the browser would pull the version of jQuery you were requesting from the cache instead of downloading it again. Everyone wins! Except the first site to request jQuery that a user hit with an empty cache.
