U2F reference implementations
U2F Authentication for Node.js
(OBSOLETE) U2F library in PHP
Python based U2F server library
Yubico Universal 2nd Factor (U2F) Host C Library
FIDO U2F support for Safari.
FIDO U2F security token support for Django
FIDO2 (WebAuthn) and FIDO U2F platform library for Linux written in Rust
Test suite for FIDO2, U2F, and other security key functions
DEPRECATED Krypton turns your Android device into a U2F Authenticator: strong, unphishable 2FA.
#IOS#DEPRECATED Krypton turns your iOS device into a WebAuthn/U2F Authenticator: strong, unphishable 2FA.