Auth0 - Auth0 is a program for people to get authentication and authorization services for their own business use.
NoPass.me - Open-source identity verification
OneLogin - On-demand SSO, directory integration, user provisioning and more
Amazon Cognito - Amazon Cognito lets you add user sign-up, sign-in, and access control to your web and mobile apps quickly and easily. It scales to millions of users and supports sign-in with social identity providers and enterprise identity providers via SAML 2.0.
Okta - Enterprise-grade identity management for all your apps, users & devices
Civic Token - Access to identity verification via the blockchain