Facial recognition is a technology capable of verifying the identity of a person through the analysis of his, or her, face. In recent years this biometric measurement has become increasingly popular: it is the most "natural" way to identify a person and it doesn't require any physical interaction with the person to be identified. Moreover, machine learning has greatly helped the development and the diffusion of face recognition, making it easier to develop and to implement. This technology can be used in a wide range of applications: for security services to prevent and detect crimes; for board checks to verify the passengers’ identity; on smartphones or computer for ID verification, also for critical application as bank account and mobile payment.