<p>Water electrolysis is hindered by the slow kinetics and high overpotentials associated with the oxygen evolution reaction (OER), which takes place at the anode. Spin manipulation in the OER is a promising approach by which to modulate the reaction pathway to improve the energetics and kinetics. To that end, application of magnetic fields in the OER has been shown to enhance performance; however, whether the underlying promotional mechanisms are spin-related or non-spin-related remains a topic of ongoing debate. In this Review we explore OER enhancement under magnetic fields and elucidate both spin-related and non-spin-related effects, examining key fundamentals and experimental practices to distinguish these effects. For spin-related mechanisms, we highlight the key effects of spins on the catalyst bulk, catalytic interface and reaction intermediate. We provide guidance for understanding whether enhancements are spin-related or not.</p>