You can also see this using curl:
curl -H "Referer: https://news.ycombinator.com/" https://cendyne.dev/posts/2025-08-15-single-sign-on-for-furries.html | grep hacker
If you remove the -H "Referer: ..." part, it will no longer contain the word "hacker".Honestly, I am a little surprised that Firefox is sending the "Referer" header. It feels like a relic from the days when we (mostly) weren't concerned with being tracked. I suppose that it must have practical uses that would break without it.