Information theory places constraints on multiplexing large low‐temperature detector arrays. We discuss these constraints, and review the state of the art of multiplexed low‐temperature detector arrays. The number of detectors read out by each output communication channel is much smaller than the theoretical maximum predicted by the Shannon‐Hartley Theorem. We discuss emerging multiplexing techniques based on Walsh code‐division multiplexing and hybrid multiplexing modulation functions that have the potential to increase the number of pixels multiplexed in each communication channel closer to the Shannon limit.