About 10 years ago I implemented cookie based sessions for a project I was working on. I had a terrible time debugging why auth was working in Safari but not Chrome (or vice-versa, can't remember). Turned out that one of the browsers just wouldn't set cookies if they didn't have the right format, and I wasn't doing anything particularly weird, it was a difference of '-' vs '_' if I recall correctly.

IIRC there is (or was?) a difference in case-sensitivity between Safari and Chrome, maybe with the Set-Cookie header? I've run into something before which stopped me from using camelCase as cookie keys.

Can't seem to find the exact issue from googling it.