This paper describes the application of adaptive user authentication based on a calculated digital footprint. The digital footprint is considered as an integrated indicator that the user is unique in its set of characteristics and behavior on the network. The main classes of digital footprint sources are marked, with the greatest attention paid to browser fingerprints. Using a mathematically supported method based on the comparison of the digital footprint, an experiment is conducted to determine the authenticity of the user in the three cases under consideration. The experiment showed that the method works correctly and successfully and can give better results by optimizing its parameters: the weights of criteria, the weights of browser fingerprints and the threshold value of user’s uniqueness.