Among other things, videos and commercials are downloaded to a mobile device for storage on the mobile device and later playout on the mobile device. The downloading includes downloading of metadata associated with the commercials and based on which the mobile device can select commercials for insertion into videos being played back to the user of the mobile device. The commercials to be downloaded are selected based on one or a combination of any two or more of the location of the user, the type of mobile device, and personally-identifiable information about a user of the mobile device.