Do not let your CDN betray you: Use Subresource Integrity
This could also be used to remove the need for a CDN for common libraries like jquery and similar resources. If the browser knows it has a file in its cache with the same properties (has, size, name) even if it come from a different site it can be pretty sure that the content is the same so no new request is needed.<p>So your site could use the cached copy of jquery (for instance) that was originally brought down to serve my site, or vice versa.