/
^(https?:\/\/)? # optional scheme
((?:[-a-z0-9._~!$&\'()*+,;=]|%[0-9a-f]{2})+ # optional username@,
(?::(?:[-a-z0-9._~!$&\'()*+,;=]|%[0-9a-f]{2})+)?@)? # or username:password@
(?:((?:(?:\d|[1-9]\d|1\d{2}|2[0-4]\d|25[0-5])\.){3}(?:\d|[1-9]\d|1\d{2}|2[0-4]\d|25[0-5])) # IPv4 address
|((?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z][a-z0-9-]*[a-z0-9])) # or dot-separated domain labels
(:\d+)? # optional port number
((?:\/(?:[-a-z0-9._~!$&\'()*+,;=:@]|%[0-9a-f]{2})+)*\/?) # path (possibly empty, may end in /, no double-// allowed)
(\?(?:[-a-z0-9._~!$&\'()*+,;=:@\/?]|%[0-9a-f]{2})*)? # optional querystring
(\#(?:[-a-z0-9._~!$&\'()*+,;=:@\/?]|%[0-9a-f]{2})*)?$ # optional fragment
/
ix