Enhanced online privacy

A system, comprising:

• one or more memory devices storing instructions;
• and
• one or more data processing apparatus that are configured to interact with the one or more memory devices, and upon execution of the instructions, perform operations including:
• assigning, to a client device and by a service apparatus, a given service identifier that uniquely represents the user in a service domain of the service apparatus;
• receiving, from a client device, tag information in a network call to the service apparatus that was generated by firing of a tag embedded in a resource of a publisher, the tag information specifying a given publisher identifier for the publisher and a client identifier that is (i) assigned to a user of the client device by the publisher and (ii) uniquely represents the user of the client device in a publisher domain of the publisher, wherein the service domain differs from the publisher domain, and the given service identifier assigned by the service apparatus differs from the client identifier assigned by the publisher;
• creating, in a data structure, a mapping of the given service identifier to the client identifier;
• receiving, from the publisher and by way of an application programming interface (API), a list of client identifiers that have been (i) assigned to a set of users by the publisher and (ii) uniquely represent each user in the set of users in the publisher domain;
• determining that the list of client identifiers received from the publisher includes the client identifier that (i) was received in the tag information, (ii) is mapped to the given service identifier in the data structure, and (iii) uniquely represents the user of the client device in the publisher domain;
• storing the given service identifier that is mapped to the client identifier in a list of matched service identifiers based on the determination that the list of client identifiers includes the given client identifier;
• receiving multiple content requests from multiple different client devices accessing services provided by the service apparatus in the service domain;
• and
• responding to the content requests based on whether the client devices provide service identifiers that are included in the list of matched service identifiers, including:
• transmitting first content reserved for the set of users that are assigned a client identifier in the list of client identifiers a corresponding service identifier that is included in the list of matched service identifiers;
• and
• transmitting second content that is not reserved for the set of users that are assigned a client identifier in the list of client identifiers in response to the content request not including the corresponding service identifier that is included in the list of matched service identifiers.

A non-transitory computer readable medium storing instructions that, when executed by one or more data processing apparatus, cause the one or more data processing apparatus to perform operations comprising:

• assigning, to a client device and by a service apparatus, a given service identifier that uniquely represents the user in a service domain of the service apparatus;
• receiving, from a client device, tag information in a network call to the service apparatus that was generated by firing of a tag embedded in a resource of a publisher, the tag information specifying a given publisher identifier for the publisher and a client identifier that is (i) assigned to a user of the client device by the publisher and (ii) uniquely represents the user of the client device in a publisher domain of the publisher, wherein the service domain differs from the publisher domain, and the given service identifier assigned by the service apparatus differs from the client identifier assigned by the publisher;
• creating, in a data structure, a mapping of the given service identifier to the client identifier;
• receiving, from the publisher and by way of an application programming interface (API), a list of client identifiers that have been (i) assigned to a set of users by the publisher and (ii) uniquely represent each user in the set of users in the publisher domain;
• determining that the list of client identifiers received from the publisher includes the client identifier that (i) was received in the tag information, (ii) is mapped to the given service identifier in the data structure, and (iii) uniquely represents the user of the client device in the publisher domain;
• storing the given service identifier that is mapped to the client identifier in a list of matched service identifiers based on the determination that the list of client identifiers includes the given client identifier;
• receiving multiple content requests from multiple different client devices accessing services provided by the service apparatus in the service domain;
• and
• responding to the content requests based on whether the client devices provide service identifiers that are included in the list of matched service identifiers, including:
• transmitting first content reserved for the set of users that are assigned a client identifier in the list of client identifiers a corresponding service identifier that is included in the list of matched service identifiers;
• and
• transmitting second content that is not reserved for the set of users that are assigned a client identifier in the list of client identifiers in response to the content request not including the corresponding service identifier that is included in the list of matched service identifiers.