Real-time in situ monitoring during chemical synthesis can provide vital clues for tracking nanoparticle synthesis, potentially leading to application-optimized reaction products with high yield and reproducibility. In this article, we demonstrate a homemade extinction spectroscopy platform that can track nanoparticle synthesis and chemical reactions with sub-ms time resolution. In the first part of the paper, we provide the various steps required for building and aligning the optical platform that can perform in situ extinction measurements. Subsequently, we employ the platform to study the growth of anisotropic gold bipyramids and nanorods. We show that adjusting the reaction temperature can significantly alter the synthesis rate. Thereafter, we use this system to track the photo-degradation of methylene blue dye using CeO2 nanoparticles and to track pH changes in solution. Finally, we have detailed the potential pitfalls that can arise while using the system and potential avenues for addressing them. In addition to the examples demonstrated here, the established platform can be used to study other reactions, including drug synthesis, protein aggregation, phase separation, and sol-gel synthesis by choosing an appropriate wavelength range of operation. The information extracted from this analysis can be used to modify the reaction conditions in real-time to obtain a pre-determined synthesis product, thereby making synthesis processes efficient and convenient.