Systems and methods are disclosed for authenticating an identity of an online user. One method includes receiving from the user, through a first device, a request to access a web page associated with the user's online account; transmitting to the user an image that contains a unique ID and a URL of an authentication server; and receiving from the user, through the first device, an authentication request containing the unique ID. The method also includes receiving from the user, through a second device, a log-in ID associated with the user and the unique ID; and authenticating the identity of the user to grant the user access, through the first device, to the web page associated with the user's online account.