Configuration of advertisements in a streaming video segment works in cooperation with a client device. Using a selection algorithm, a server selects a first number of default video advertisements for a video streaming session, and a second number of alternative video ads greater than the first number. The server provides identifiers for the alternative video advertisements and transmits the identifiers to the client device prior to a corresponding ad break in the streaming video. During or before streaming of one of the default video advertisements to the client device, the server detects a signal from the client device requesting that one of the alternative video advertisements be swapped for the one of the default video advertisements, interrupts streaming of the default video, and initiates streaming of the one of the alternative video advertisements, in response to detecting the signal. Corresponding operations may be performed by the client device.