Bio-inspired computing architectures enable ultralow power consumption and massive parallelism using neuromorphic computing, which is apt to implement Spiking Neural Networks (SNN). Such architectures are particularly suitable for energy-constrained applications. A deeper understanding of Spiking Neural Networks (SNN) behavior during training is needed to improve these architectures. This paper presents VS2N, a web-based tool for interactive visualization and analysis of SNN activity over time. This simulator-independent tool offers a way to examine, analyze and validate different hypotheses about SNN activity. We present available analysis modules and use-cases of the tool as an example.