Techniques are described for promoting content items in a page to load in a different order than the order in which they were initially designated to load in the page. A page may include critical content items designated to load earlier than non-critical content items. In instances where there is a delay due to latency in generating or retrieving the critical content items, one or more non-critical content items may be promoted to load earlier than initially designated. By promoting non-critical content items to load during the period in which the loading of the page may otherwise be stalled, overall page load times may be reduced. Content transport may employ a multi-stream networking protocol that multiplexes a plurality of streams, and promotion may include writing to a particular stream during the delay in availability of the critical content items.