This memo presents the FQ-CoDel hybrid packet scheduler/AQM algorithm, a powerful tool for fighting bufferbloat and reducing latency. FQ-CoDel mixes packets from multiple flows and reduces the impact of head of line blocking from bursty traffic. It provides isolation for low-rate traffic such as DNS, web, and videoconferencing traffic. It improves utilisation across the networking fabric, especially for bidirectional traffic, by keeping queue lengths short; and it can be implemented in a memory- and CPU-efficient fashion across a wide range of hardware.