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The growing needs in monitoring health and environmental risks call for the development of smart ultraviolet (UV) photodetectors with special or multiple functions. Herein, a photoelectrochemical cell based self‐powered and wearable UV photodetector system with high stability, high speed, and an interesting visualization feature is successfully developed. TiO2 nanotubes on flexible Ti foil and Prussian blue on flexible polyethylene terephthalate/indium‐tin oxide are selected as the photoanode and electrochromic counter electrode, respectively. The integrated flexible UV photodetectors can not only function stably for many bending cycles but also exhibit visualized indication of UV exposure by recyclable color change without external power. Moreover, the as‐fabricated visible‐blind photodetectors show excellent UV responsivity (78.3 mA W−1), ultralow UV light detection limit (<10 µW cm−2), and fast response with a rise time and a decay time of 0.04 and 0.06 s, respectively. Our all‐in‐one smart photodetector has demonstrated great application potential in self‐powered smart sensors and wearable healthcare electronics. An all‐in‐one visualized, self‐powered, and wearable UV photodetector is successfully developed. The self‐powered and wearable photodetector shows excellent UV responsivity, an ultralow detecting limit, and fast response performance. Strikingly, the UV intensity can be visually judged by the degree of decoloration and also provides visualized indication of UV exposure by recyclable color change. [ABSTRACT FROM AUTHOR]