In general, the subject matter described in this disclosure can be embodied in methods, systems, and program products for sending image data to a client device. The computing system sends first image data from which a computing device is able to generate an initial display of an image. The initial display is a reduced-resolution version of the image that is reduced in resolution in comparison to a full resolution of the image. The computing system sends second image data from which the computing device is able to generate a subsequent display of the image. The subsequent display of the image is an intermediate-resolution version of the image that has a resolution that is higher than a resolution of the reduced-resolution version of the image and that is lower than the full resolution of the image.