How do I reset safari to a state equal to that of a new user? There is a website (happening.im) which does not work in my user account, but does work when I switch to the guest user.
So the problem is in my user profile somehow.

I've tried deleting ~/Library/Safari but that didn't do the trick.

How do I completely reset safari to the state that the guest user has?
This website has a list of steps you could take:
http://www.macissues.com/2015/06/22/how-to-fully-reset-safari-on-your-mac/