There is currently great interest in developing an environment-friendly, low-cost, and scalable approach for producing stimuli-responsive fluorescent hydrogels (FHs) with excellent mechanical property, rewritable fluorescence, and dual anti-counterfeiting capabilities. Herein, by applying natural, environment-friendly, and sustainable curcumin as a responsive agent, tough pH-responsive FHs (pH-FHs) are fabricated via a facile preparation strategy. These materials have outstanding mechanical performances: ultimate stress of 180 kPa, an ultimate strain of ~2500%, and good anti-fatigue performances against compression. These pH-FHs are able to sense ammonia and formaldehyde gas, resulting in both a color change and fluorescence for dual anti-counterfeiting functionality. This sensing information is stored individually by the pH-FHs and could be externally removed using formaldehyde gas to achieve a rewritable system. Our study provides valuable insights that are expected to facilitate the development of smart FHs for information encryption and anti-counterfeiting applications.