Tannic acid (TA) is extensively employed in daily life. However, excessive intake of TA may potentially jeopardize human health. Thus, there arises an urgent need for rapid and sensitive detection of TA. This study presents the development of a smartphone-assisted fluorescence platform for the detection of TA using a Tb metal-organic framework (Tb-MOF). The presence of TA led to significant fluorescence quenching of Tb-MOF due to the competitive absorption. Furthermore, this sensor was successfully applied for the detection of TA in real samples such as wines and juices with recoveries ranging from 98.70 % to 102.22 %. Visual test strips based on Tb-MOF were developed for accurate TA detection through RGB signal analysis.