Coding, in the binary communications world, is the process of adding a bit or bits to useful data bits in such a fashion as to facilitate the detection or correction or errors incurred by such useful bits as a result of their transmission over a non-ideal channel. Such a channel, for example, may be one that adds noise, or interference, or unwanted nonlinearities. In this chapter, we focus on error detection and error correction coding as applied to user data in 5G/5G-Advanced, Wi-Fi 6/7, and Bluetooth 5/6, including low-density parity check (LDPC) coding, binary convolution code (BCC) coding, and hybrid automatic repeat request (HARQ). Error detection on its own obviously does nothing to improve error rate performance. However, as we shall see, it can aid in error correction when combined with other techniques.