In a real-time collaboration server, a control unit manages a collaboration mode. The control unit operates a virtual client that maintains a virtual screen reflecting the status of the collaboration (e.g., the contents of a shared desktop or whiteboard). The virtual client renders collaboration data within the virtual screen. New clients are synchronized with an ongoing collaboration by packing and sending them a copy of the virtual screen. The control unit maintains a queue of collaboration data to be sent to participating clients. Each client may have a pointer identifying the queued data it is processing. The queue may be collapsed (e.g., when it reaches a maximum size) by sending a copy of the virtual screen to one or more clients that have not yet consumed old data in the queue; those clients are then updated to skip the queue entries embodied in the virtual screen.