Patent attributes
Features are disclosed for modifying identifying data including, but not limited to, demographic information, user identifiers, and device identifiers, according to user-definable preferences prior to transmitting content requests to content servers. The information may be modified to protect a user's privacy. In addition, the modified information may allow the content provider to serve a customized or targeted version of content that is more relevant to the user than a version that may otherwise be generated without the aid of identifying data. Users may elect to share some, all, or none of their identifying data with content providers, or users may elect to generalize their specific identifying data. Additional features include providing generalized or customized identifying data to cooperating content providers. Custom headers and other data fields may be provided to content providers, and content providers may choose to use information in the custom data fields or ignore it.