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Labels based on physical unclonable functions (PUFs) have been proven to be some of the most effective anticounterfeiting strategies. However, it is still challenging to develop PUF-based anticounterfeiting labels with low prices, simple manufacturing, and easy authentication. Herein, photochromic PUF labels are fabricated by randomly dispersing highly crystalline carbon nitride (HCCN) particles in poly(vinyl acetate) (PVAc). The color of the PVAc/HCCN films originating from photochromism is used as the first layer of safety, which is verified by the naked eye. The pattern of the randomly distributed HCCN particles within the photochromic area (i.e., the PUF) is used as the second layer of security. The PUF can be read out by any smartphone equipped with a portable objective and then automatically authenticated by computer vision technology. We further prove the accurate and feasible authentication of the prepared PUFs and their application potentials.