Decentraleyes – Local CDN Emulation
After clicking through several more times and ending up in a gitlab wiki, this seems to be how it works:>  It comes bundled with a fair amount of commonly used files, and serves them locally whenever a site tries to fetch them from a delivery network.The docs, both on the site that is linked to and on the wiki is extremely bare bones, but the gist of it is that a CDN can track you through the `referer` header of the request for (say) jquery, since even if the browser has jquery already cached it will send out a request to check if the resource might have been modified.