Purpose: Recent research has demonstrated that europium doped potassium chloride (KCl:Eu2+) storage phosphor material has the potential to become the physical foundation of a novel and reusable dosimetry system using either film‐like devices or devices similar to thermoluminescent dosimeter chips. In this work, we will quantify the low dose detection resolution of the KCl:Eu2+ prototype dosimeter and demonstrate how it can be incorporated into clinical application for in vivo peripheral dose measurements. Methods: The prototype KCl:Eu2+ dosimeters used in this study were manufactured according to standard materials processes, and had a physical makeup similar to thermoluminescent dosimeter chips. The lowest dose‐to‐water of 0.01 cGy in this work was achieved underneath a fully closed multileaf collimator at a source‐to‐surface distance of ∼200 cm. For doses greater than 100 Gy, prototype dosimeters were irradiated using the XRLM4 beamline at the Center for Advanced Mircrostructure and Devices synchrotron facility at Louisiana State University in Baton Rouge, LA. To compare sensitivity, two commercial storage phosphor detectors were also irradiated under the same conditions. The dosimeters were read using a laboratory photostimulated luminescence detection system. Results: KCl:Eu2+ prototype storage phosphor dosimeter is capable of measuring a dose‐to‐water as low as 0.01 cGy from a 6MV photon beam with a signal‐to‐noise ratio greater than 6. Agfa MD10, Fuji STIII and KCl:Eu2+ prototypes were within 10% in sensitivity. A pre‐readout thermal annealing procedure enables the dosimeter to be read within an hour post irradiation. The dosimeter retains a constant response after receiving large accumulated doses (∼10 kGy). The energy‐dependence encountered during low dose peripheral measurements can be accounted for via a single point outside‐field calibration per each beam quality. Conclusions: With further development the KCl:Eu2+− based dosimeter could become a versatile and durable dosimetry tool with large dynamic range (sub‐cGy to 100 Gy). This work was supported in part by NIH Grant No. R01CA148853.