Systems and methods for detecting device or carrier change conversions based on device information and carrier information that is received with requests to provide content to communication devices is provided. A system can receive requests to provide content including a device identifier, an account identifier identifying an account agnostic to the device, and a carrier identifier. The system can serve content items in response to the requests to provide content that are related to communication devices different from the device associated with the device identifier or carriers different from the carrier associated with the carrier identifier. The system can detect, from the contents of a subset of the requests to provide content, that the account identifier is associated with a different device identifier or carrier identifier and identify one or more content items corresponding to the different device identifier or carrier identifier. The system can then attribute credit for the change in device identifier or carrier identifier to the identified content items.