Herein, we have studied and reported the effect of various activating agents/temperature and precursor impregnation ratio on the porosity of mangosteen shell (M-S) derived activated carbons. The as-produced samples were characterized by using various technique such as scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and N₂ physisorption analysis among others. These characterization techniques enabled the determination of the optimum technological parameters for preparing the M-S activated carbon via atmospheric pressure chemical vapour deposition (APCVD) technique. Electrochemical performances of the samples performed via a three-electrode measurement revealed a specific capacitance of 298.13 F g^-1 at a specific current of 0.5 A g^-1 at a potential window of -0.8 V using 2.5 M KNO₃ as the electrolyte. An assembled symmetric M-S AC//M-S AC device utilizing the mangosteen shell (M-S) derived activated carbon as both positive and negative electrodes using 1-Ethyl-3-methylimidazolium-bis(fluoroSulfonyl)imide ionic liquid electrolyte in a wider potential window of 2.8 V gave a specific capacitance of about 28.02 F g⁻¹ at 0.5 A g⁻¹ corresponding to a specific energy of 30.51 Wh kg⁻¹ and a specific power of 194.44 W kg⁻¹. The device proved an excellent cycling stability over a cycling test of 20,000 charge/discharge cycles conducted within an operating potential of 2.8 V at a specific current of 5 A g^-1.