Perovskite photodetectors (PDs) with tunable detection wavelength have attracted extensive attention due to the potential application in the field of imaging, machine vision, and artificial intelligence. Most of the perovskite PDs focus on I- or Br-based materials due to their easy preparation techniques. However, their main photodetection capacity is situated in the visible region because of their narrower bandgap. Cl-based wide bandgap perovskites, such as CsPbCl , are scarcely reported because of the bad film quality of the spin-coated Cl-based perovskite, due to the poor solubility of the precursor. Therefore, ultraviolet detection using high-quality full inorganic perovskite films, especially with high thermal stability of materials and devices, is still a big challenge. In this work, high-quality single crystal CsPbCl microplatelets (MPs) synthesized by a simple space-confined growth method at low temperature for near-ultraviolet (NUV) PDs are reported. The single CsPbCl MP PDs demonstrate a decent response to NUV light with a high on/off ratio of 5.6 × 10 and a responsivity of 0.45 A W at 5 V. In addition, the dark current is as low as pA level, leading to detectivity up to 10 Jones. Moreover, PDs possess good stability and repeatability.