1. A system, comprising: a data processing apparatus; and a computer storage medium encoded with a computer program, the program comprising data processing apparatus instructions that when executed by the data processing apparatus cause the data processing apparatus to perform operations comprising: receiving from a client device a request for a search resource; providing to the client device in response to the request for the search resource, the search resource including interface instructions that cause the client device to generate a search interface that includes a query input field; receiving query suggestion requests from a client device, each query suggestion request having been generated in response to a query input in the query input field; in response to each query suggestion request: providing query suggestions responsive to the request; determining if a prediction criterion is met, the prediction criterion being independent of a user selection of a query suggestion provided in response to one or more query suggestion requests and independent of receiving a completed query from the client device; in response to determining that the prediction criterion is met, providing search results to the client device, the search results being responsive to one of the query suggestions provided in response to the query suggestion request or one or more previous query suggestion requests; and in response to determining that the prediction criterion is not met, not providing the search results to the client device.