Its purpose is just to keep the same scheme/protocol. So http goes to http, https goes to https.

If the original URL was http and you receive a redirect "//forums.mirc.com/ubbthreads.php/forum_summary" the new effective url would be http://forums.mirc.com/ubbthreads.php/forum_summary
If the original URL was https with the same redirect "//forums.mirc.com/ubbthreads.php/forum_summary" the new effective url would be https://forums.mirc.com/ubbthreads.php/forum_summary


You can see this forum does it on a redirect, if you look at the source of https://www.reddit.com you can see a bunch of resources use this format href="//


https://tools.ietf.org/html/rfc1808


Quote
URL = ( absoluteURL | relativeURL ) [ "#" fragment ]

absoluteURL = generic-RL | ( scheme ":" *( uchar | reserved ) )

generic-RL = scheme ":" relativeURL

relativeURL = net_path | abs_path | rel_path

net_path = "//" net_loc [ abs_path ]
abs_path = "/" rel_path
rel_path = [ path ] [ ";" params ] [ "?" query ]

Last edited by Loki12583; 20/10/20 12:25 PM.