Authentication

What Are Authentication APIs?

Authentication APIs handle the hardest part of user account security so you don't have to rebuild it yourself. A secure auth system requires correct implementation of OAuth 2.0 flows, PKCE, token rotation, session management, brute-force protection, MFA, and compliance with regulations like GDPR and SOC 2 — all areas where subtle bugs cause serious breaches. Managed auth APIs do all of this correctly, out of the box, so your team can focus on your actual product.

What Developers Implement

• Social login with Google, Apple, GitHub, and 30+ other providers via OAuth 2.0
• Passwordless authentication using magic email links or one-time codes
• Passkey (WebAuthn) support for phishing-resistant biometric login
• Time-based OTP (TOTP) and SMS-based multi-factor authentication
• Machine-to-machine authentication with JWT and API key management
• Enterprise SSO via SAML 2.0 and OIDC for B2B SaaS customers

Choosing the Right Auth Provider

Clerk leads on developer experience — React components, Next.js SDK, and a generous 10,000 free MAU limit make it the fastest integration for modern web apps. Supabase Auth is the lowest-cost option at $0.00325/MAU after 50,000 free users, and it bundles with Supabase's database and storage. Auth0 by Okta is the enterprise standard with HIPAA BAA, FedRAMP compliance, and the widest library of enterprise identity providers. Firebase Authentication is the default for mobile-first apps already in the Google ecosystem. All four offer free tiers sufficient for most early-stage products.