1. A computer-implemented method, comprising: determining completions for prefixes, wherein a prefix represents a portion of a search query and each completion represents a suggestion for completing the prefix and yielding a completed search query; identifying one or more content items for each determined completion; generating content item-completion pairs for the determined completions, each content item-completion pair being a pair of a determined completion and a content item identified for the determined completion; receiving user input in a control associated with a search engine, the user input including a series of input characters defining a prefix that when completed would form a completed search query; evaluating the characters of the prefix to identify one or more completions for the prefix; matching the one or more completions to one or more previously generated content item-completion pairs; identifying display data associated with the content item for a matching content item-completion pair for transmission to a user device along with one or more completions in response to receiving the user input; and providing, prior to a completed search query associated with the prefix being submitted to the search engine in a search request, the display data and the one or more completions to the user device, wherein the content item of the matching content item-completion pair is displayed proximate to a completion of the matching content item-completion pair on the user device.