Pass a char * as parameter, pointing to a zero terminated login details string
for the connection. The format of which is: [user name]:[password].
When using Kerberos V5 authentication with a Windows based server, you should
specify the user name part with the domain name in order for the server to
successfully obtain a Kerberos Ticket. If you dont then the initial part of
the authentication handshake may fail.
When using NTLM, the user name can be specified simply as the user name
without the domain name should the server be part of a single domain and
To specify the domain name use either Down-Level Logon Name or UPN (User
Principal Name) formats. For example, EXAMPLE\user and firstname.lastname@example.org
Some HTTP servers (on Windows) support inclusion of the domain for Basic
authentication as well.
When using HTTP and CURLOPT_FOLLOWLOCATION(3), libcurl might perform
several requests to possibly different hosts. libcurl will only send this user
and password information to hosts using the initial host name (unless
CURLOPT_UNRESTRICTED_AUTH(3) is set), so if libcurl follows locations to
other hosts it will not send the user and password to those. This is enforced
to prevent accidental information leakage.
Use CURLOPT_HTTPAUTH(3) to specify the authentication method for HTTP
based connections or CURLOPT_LOGIN_OPTIONS(3) to control IMAP, POP3 and
The user and password strings are not URL decoded, so theres no way to send
in a user name containing a colon using this option. Use
CURLOPT_USERNAME(3) for that, or include it in the URL.