The disclosure relates generally to providing synchronized supplemental content. In one aspect, second user devices may be used to consume supplemental content associated with primary content presented on a first display. The supplemental content may be synchronized with the primary content. Such synchronization may be performed by detecting and reporting triggers within the primary content and transmitting synchronization signals to appropriate second user devices. Another aspect of the disclosure relates to determining which interfaces or applications will report the triggers, and fine-tuning how many interfaces or applications will report the triggers.