2 Factor Authentication Tools provide an extra layer of security when trying to verify identity of a user. Most systems do this based on a username and password. However, 2 Factor Authentication uses and additional layer of security by using an SMS or Email in addition to the standard security features of a username and password. Analyzo has listed the best 2 Factor Authentication Services in US that you can use to add an additional layer of security to your application. Click on Quick View to see plan features or compare plans across companies.