The maturation of many photonic technologies from individual components to next-generation system-level circuits will require exceptional active control of complex states of light. A prime example is in quantum photonic technology: while single-photon processes are often probabilistic, it has been shown in theory that rapid and adaptive feedforward operations are sufficient to enable scalability. Here, we use simple “off-the-shelf” optical components to demonstrate active multiplexing—adaptive rerouting to single modes—of eight single-photon “bins” from a heralded source. Unlike other possible implementations, which can be costly in terms of resources or temporal delays, our new configuration exploits the benefits of both time and space degrees of freedom, enabling a significant increase in the singlephoton emission probability. This approach is likely to be employed in future near-deterministic photon multiplexers with expected improvements in integrated quantum photonic technology.