Methods, systems, and apparatus, for detour based content selection. In one aspect, a method includes receiving, at a data processing apparatus, location data for a plurality of users, the location data describing, for each user, locations of a user device of the user; determining, from the location data, route data for the plurality of users, the route data describing, for each user, a route traveled by the user; determining, by the data processing apparatus, for at least one or more of the users, a detour from the route traveled by the user to a retail location of the offeror; determining, by the data processing apparatus, for each of the at least one or more of the users, whether the user is eligible for an offer of the offeror based on the detour; and for each user eligible for an offer, enabling the offeror to provide an offer to the user.