With 13,800 GitHub stars, adoption by OpenAI for ChatGPT's authentication infrastructure serving 800 million weekly active users, and governance under the Ory open-source ecosystem, Ory Kratos provides enterprise-grade identity management as a headless API server that separates authentication logic from user interface — enabling any frontend framework to consume standardized self-service flows for registration, login, recovery, verification, and profile management. Multi-factor authentication supports passkeys, WebAuthn security keys, TOTP authenticator apps, SMS one-time codes, email magic links, and backup recovery codes with configurable Authenticator Assurance Levels enforcing step-up authentication for sensitive operations. Social sign-in connects to any OpenID Connect provider including Google, GitHub, Apple, and Microsoft, plus enterprise SAML 2.0 federation for B2B single sign-on. Customizable identity schemas using JSON Schema define user profiles with flexible trait structures, while pre- and post-flow webhooks enable integration with CRMs, analytics, and compliance systems. The courier system handles email and SMS delivery for verification codes and password recovery links. Session management provides device tracking, forced logout, and configurable lifespans with privileged session elevation. Deploy alongside Ory Hydra for OAuth2/OIDC token issuance and Ory Keto for fine-grained permissions to build a complete identity platform. Docker Compose deployment with PostgreSQL. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. Apache 2.0 licensed.

With over 14,000 GitHub stars, 1 million managed identities on Logto Cloud, and continuous releases through version 1.42.0 in July 2026, Logto has emerged as the most credible open-source alternative to Auth0, Clerk, and AWS Cognito by packaging OIDC, OAuth 2.1, enterprise SSO, multi-tenancy, and RBAC into a single MPL-2.0 codebase that self-hosts for free with no per-MAU pricing surprises. Every Logto tenant operates as a fully compliant OpenID Provider supporting PKCE-only public clients, DPoP token binding, and RFC 9068 JWT access tokens. Pre-built sign-in flows handle email, phone, social login via Google, Facebook, Azure AD, and dozens of connectors, passkey authentication, and multi-factor verification through TOTP and WebAuthn. Organizations enable first-class multi-tenancy where users belong to multiple tenants with per-organization RBAC scopes on API resources. Enterprise SSO connects to Okta, Entra ID, and any SAML or OIDC identity provider. SDKs for over 30 frameworks including React, Next.js, Angular, Vue, Flutter, Go, and Python integrate authentication into SPAs, web apps, mobile apps, APIs, machine-to-machine, and CLI tools. The admin console provides user management, audit logs, webhook event subscriptions, and custom domain configuration. Personal Access Tokens and token exchange support AI agent architectures and MCP server authentication. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MPL-2.0 licensed.

With 13,800+ GitHub stars and active releases through 2026, Casdoor is the open-source identity platform that ships OAuth 2.0, OIDC, SAML 2.0, CAS, LDAP, SCIM 2.0, WebAuthn passkeys, TOTP multi-factor authentication, and Face ID biometric login in a single Go binary with a React web console — covering every authentication protocol your organization will ever need. Social login connects 50+ identity providers including Google, GitHub, Microsoft Azure AD, Facebook, WeChat, DingTalk, Apple, Twitter, and LinkedIn without custom code. The AI-first architecture includes a Model Context Protocol gateway for AI agent authentication and Agent-to-Agent protocol support for securing LLM-powered workflows. Built-in Casbin integration delivers authorization primitives beyond basic RBAC: attribute-based access control, relationship-based access control, and custom policy models through a unified engine. The organization-scoped multi-tenancy model isolates users, applications, and identity providers per tenant with customizable login pages, branding, and SMTP configuration. SCIM 2.0 endpoints automate user provisioning from HR systems and Active Directory. Official SDKs for Go, Java, Node.js, Python, and PHP accelerate application integration. The RESTful API exposes every resource for programmatic management. Comprehensive audit logs record authentication events and administrative actions. Deploy via Docker Compose with MySQL or PostgreSQL, the all-in-one SQLite Docker image for quick trials, or the official Kubernetes Helm chart for production clusters. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. Apache 2.0 licensed.