Understanding proton dynamics in the diffusion layers generated by metal electrodeposition processes is of prime importance from the point of view of knowledge-driven technology development. Here we introduce a simple, non-invasive p H-sensing approach that is based on the Tyndall effect enhancement modulated by p H-controlled agglomeration events. We employ a laser beam laterally aligned to an electrode surface where cobalt deposition and hydrogen evolution take place simultaneously. This configuration allows the visualization of p H changes that result in precipitate formation and that extend to greater distances over patterned surfaces compared to flat ones, demonstrating a p H-guiding effect in superconformal metal deposition. The method provides real-time visualization of the p H dynamics with high lateral spatial resolution (50 μ m) without physically or chemically influencing the investigated system. We suggest that applicability of the method can be extended to other processes where nanoaggregation/decomplexation inherently occur, as part of the investigated phenomena, at light-addressable interfaces.