So today I was trying to get SSL working on my machine with localhost. In the process I set the HSTS headers, telling the browser to never access the non-secure
http:// version of localhost. Thus going to
http://localhost:4000 would always fail as HSTS tells the browser to only access
Here is how you can reset the cache Safari has for HSTS pinnings so you can access your local
Open a terminal and follow those steps:
sudo killall nsurlstoraged # or edit file, search for "localhost", remove it and then save rm -f ~/Library/Cookies/HSTS.plist launchctl start /System/Library/LaunchAgents/com.apple.nsurlstoraged.plist
You may have to restart Safari afterwards.