Auth0

Auth0, now part of Okta, is an identity-as-a-service platform that offloads authentication and authorization infrastructure from application teams. Its architecture centers on a multi-tenant identity fabric that exposes OAuth 2.0, OpenID Connect, and SAML endpoints, backed by configurable Identity Providers (social, enterprise, database, passwordless) and a rules/Actions runtime for extending token issuance logic with server-side JavaScript. Core primitives include the Universal Login hosted page, the Management and Authentication APIs, and a tenant-level configuration model spanning Applications, APIs (Resource Servers), Connections, and Organizations for B2B multi-tenant scenarios. Engineering teams use Auth0 to implement login flows, single sign-on, MFA, passwordless, and machine-to-machine token exchange without building and maintaining a credential store or token service. It supports standard protocols (OAuth2, OIDC, SAML, WS-Fed) and ships SDKs for SPA (auth0-spa-js, React, Angular, Vue), native/mobile (iOS Swift, Android Kotlin, React Native), and backend frameworks (Node.js, ASP.NET, Java, Python, PHP, Go), plus Terraform and Deploy CLI for infrastructure-as-code tenant management. Auth0 Actions (successor to Rules/Hooks) allow custom logic—claims enrichment, risk-based step-up, external API calls—to run in a sandboxed Node environment during login, token issuance, and pre-user-registration flows. The target audience ranges from solo developers needing a quick social login integration to enterprise platform teams building customer-facing (B2C) or business-facing (B2B) identity layers requiring SAML federation, custom domains, and compliance certifications (SOC 2, HIPAA, ISO 27001). Its extensibility model and Organizations feature make it particularly suited for multi-tenant SaaS products needing per-customer branding, IdP federation, and role-based access control at scale.