Clef was a San Francisco-based technology company, known for developing a mobile app that created a two-factor authentication for websites.
[3][4] It had a standard verification method that requires access to data on the mobile phone to confirm the user's identity.
[5][6] The application required a Wi-Fi or mobile network, and the user could log in by scanning the computer screen with their phone.
[7][8] Clef was founded in 2013 by Mark Hudnall, B. Byrne and Jesse Pollak.
[11] Clef integrated with many websites and applications, including WordPress.