PIXELSERVER Using NGINX
Replace IP-Addresses "1.1.1.1" and "1:1:1::1" with your servers IP Addresses. Use your (RPZ) DNS Server to redirect blocked sites to those IP-Addresses (see: https://github.com/cbuijs/rpz-scum-blocker).
This configuration will return an empty image, HTML or file based on the request, with the correct codes. Browser will cache this and will speed up browsing dramatically.
Disclaimer: Provided as is. No guarantees it will not break anything.