Notices by Daniel (dan@freeradical.zone)

@aral this wording mentioning 'receiver' makes me feel like a Proxy instance was involved, but they're not really used much outside testing frameworks I think :P

@aral glad I could help :)
On the topic of TLS I was about to suggest a wildcard certificate `*.localhost` but it turns out that's not allowed by browsers 😅 via https://stackoverflow.com/a/68514822/3582903

@aral There's also subdomains of localhost e.g. instance1.localhost
& instance2.localhost. I'm not sure if Firefox implements that, but Chrome will always resolve subdomains of localhost to localhost.
You could also run a proxy (caddy, nginx, etc) on 443 and have it send the different subdomains/IPs to the different instances.
Yea, cookies are effectively just host+path :)