Top 9 Authentication & Authorization APIs For Developers - Public APIs

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Authentication & Authorization

Auth0
Easy to implement, adaptable authentication and authorization platform.
Clerk
Drop-in React components for authentication and authorization.
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Corbado
Passkey-first authentication.
GetOTP
Implement OTP flow quickly.
Kinde
Authentication for modern applications. Integrates in minutes and free up to 7,500 MAU.
MojoAuth
Secure and modern passwordless authentication platform.
ReqKey
ReqKey validates API keys, meters credits, enforces rate limits, and logs every request — from a single SDK call inside your own middleware.
Stytch
User infrastructure for modern applications.
Warrant
APIs for authorization and access control.

Guides

September 18, 2026
Best Auth0 Alternatives in 2026, RankedThe best Auth0 alternatives in 2026, ranked, with every free tier and open-source repo checked in September 2026. The headline user allowances do not compare.