Abstract: A method of monitoring media playback includes outputting media content from a server over a network to a client device, and receiving at the server from the client device, a plurality of beacon signals, each beacon signal having at least one pair of timing data items. A first data item in the pair represents a point in time in the media content and a second data item in the pair represents a time indicated by a real time clock of the client device at which time the part of media content corresponding to the point in time was being played by the client device. The at least one of processed or stored beacon signals are at the server so as to monitor the playback of the media content by the client device.