That’s still header filtering. And it should be X-CF- by the way.

It took me about 10 years to hear about it, but the IETF tried to deprecate the X- prefix back in 2012: https://datatracker.ietf.org/doc/html/rfc6648

Good to know.

(Also sibling is right, I spaced on X-CF- being a header sent to CF customers’ servers. I don’t used cloudflare but cloudfront does the exact same thing)

X-CF- seems to be used by some other software. And Cloudflare has plenty of documented headers that don’t start with X.

The whole point is that a genuine user header should never conflict with a Cloudflare internal header, and a browser should never see an internal header.

Having re-read the thread, I totally agree. What you have listed is table stakes. I'd also say that internal headers would also be encrypted to a narrow protection domain.

If all internal headers were prefixed with X-CF-, you could strip them all via SIMD that had no knowledge of any specific header. Hell, you could probably do it on the NIC.

Please reread the entire thread. We are talking about someone who thinks the header solution is stupid. You are both splitting hairs. Stay on target.