Long: proxy-user Short: U Arg: <user:password> Help: Proxy user and password --- Specify the user name and password to use for proxy authentication. If you use a Windows SSPI-enabled curl binary and do either Negotiate or NTLM authentication then you can tell curl to select the user name and password from your environment by specifying a single colon with this option: "-U :". If this option is used several times, the last one will be used.