[hotpotamus]

Is there an actual RFC for that? I was thinking it was just browsers (Google really) who enforced it by convention.

[banana_giraffe]

As I understand it, it is just browsers enforcing it, with Safari [1] doing so first, then Chromium [2] doing the same, both doing so in 2020.

[1] https://support.apple.com/en-us/102028

[2] https://chromium.googlesource.com/chromium/src/+/master/net/...