From IndieWeb

SQRL is the acronym to "Secure Quick Reliable Login".

SQRL (pronounced “squirrel”) is an open, free, intellectual property unencumbered, complete and practical system to cryptographically authenticate the identity of individuals across a network. Though principally intended for website visitor identification and account sign-in, its concepts may be extended for related applications. SQRL may be used alongside other traditional website sign-in systems, and it can replace all other systems while offering dramatic improvements in usability and security.

Though designed and intended to be a two-party solution – website visitor to website – if needed, SQRL can also be used in a federated third-party mode to provide centralized identity management services to websites (e.g. login.gov).

SQRL supports sign-in on a device containing the SQRL client, and “cross-device” sign-in using a SQRL client on a separate device, such as a smartphone, in the role of secure identity authenticator. SQRL clients currently exist for Windows, Linux/Mac (via WINE), Android, iOS, Chrome, Firefox, Edge.

Official website