A device fingerprinting system provides an additional factor of authentication. A user device may be redirected, along with user ID parameters, to authentication system. The user device may be sent instructions to execute that collect and send back device characteristic information to the authentication system. The authentication can create a unique fingerprint of the device, and determine if the fingerprint has been seen before. If seen before, the authentication system may send back an authentication token indicating the additional factor of authentication was a success. If the fingerprint has not been seen previously, the authentication system may conduct a one-time password authentication as the additional factor. If successful, the fingerprint may be stored in association with the user device for future authentication as an additional factor.