**Abstract:** Electrocatalyst deactivation poses a significant obstacle in transitioning water electrolysis technology from laboratory-scale to industrial applications. To inspire more effort on this topic, this contribution explores the structural factors contributing to catalyst deactivation, elucidating the underlying mechanisms with detailed case studies of hydrogen and oxygen evolution reactions. Specifically, the in situ assessment and characterization techniques are highlighted, which can offer a collective understanding of catalyst deactivation. Building on these insights, recent advances in mitigating catalyst deactivation are introduced, from innovative catalyst designs to advanced electrode engineering. The review concludes by emphasizing the necessity for universal test protocols for deactivation and integrating evidence from diverse in situmeasurements, aiming to provide introductive guidance examining the complexities of electrocatalyst deactivation.