Emulsions, consisting of liquid droplets suspended in an immiscible liquid, are crucial in industries such as food, pharmaceuticals, and oil extraction. A key challenge in emulsification is controlling droplet breakup, which influences the stability and rheology of the suspension. This study explores the dynamics of droplet fragmentation in shear flow, focusing on the effects of viscosity and confinement. Utilizing a phase-field approach, which replaces a sharply defined interface with a diffuse one, we investigate how confinement and viscosity ratios impact droplet breakup. Under moderate confinement, droplets exhibit a characteristic “pinching” in the middle, forming equal-sized daughter droplets and a small satellite droplet (Breakup mode I). As confinement increases, fragmentation occurs predominantly in the central region of elongated droplets (Breakup mode III). Higher viscosity ratios cause fragmentation mainly at the edges, preserving the droplet center (Breakup mode II). These findings provide valuable insights into the role of confinement and viscosity in droplet breakup, helping to optimize conditions for applications such as emulsion production and the fabrication of polymeric fibers. This work is crucial for advancing the design of smart materials and understanding the fundamental mechanics of droplet fragmentation.