Replacement of content items

The subject matter of this specification can be embodied in, among other things, a method that includes receiving a user account identifier of a content item suppression account and an identity of a user-specified content item, receiving an auction announcement message including the user account identifier and a request for allocation of a content item to a content inventory unit to be presented at the user device, determining a bid for presenting the content item in place of third-party content, transmitting the bid to the auction platform, transmitting the content item in response to the auction announcement message, receiving a message indicating that the content item has been presented in place of the third-party content and an auction price for presenting the content item in place of the third-party content, and reducing a stored account value associated with the user account identifier based on the auction price.