What are the allowed web links for external websites for the Link field?

I've noticed that there is a ltitle globe icon that shows green for a valid link or red for an invalid one. Can someone please tell me the requirements for this? For example I can put in google, reddit and youtube just fine but a client wants to put in https://xxx.xxx.xxx.uk/user-application?role=Member - Associate (20%) which is causing an error crash on my server.

Are the parenthesis or spaces causing issue here?

Hey @sog, the web link needs to be a complete URL. There seems to be an excess space at the very end - Associate (20%) What's the entire URL you're trying to add?