Authentication APIs
Authentication and authorization services
This directory lists 5 authentication APIs. Use the filters below to narrow by authentication, HTTPS support and CORS. Every entry shows whether it needs authentication, serves over HTTPS and allows cross-origin requests, so you can pick one that fits your stack before you read a single doc page.
Best Authentication APIs for Developers
An authentication API allows developers to implement secure user login, OAuth social sign-in, multi-factor authentication, and identity management without building these complex systems from scratch. These APIs handle token issuance, session management, and user verification.
Auth0 and Stytch are the strongest starting points for most teams: Auth0 covers social, passwordless and enterprise login with a free tier up to 25,000 monthly active users, while Stytch gives a passkeys and OTP first API with 10,000 free monthly active users. MojoAuth focuses narrowly on passwordless login and is easy to bolt onto an existing app without replacing a whole identity system. GetOTP suits teams that only need one time password delivery over SMS, voice or messaging apps across many countries, not full user management. Warrant's authorization model lives on inside WorkOS FGA for teams needing fine grained permissions rather than login itself.
The pitfall here is vendor lock in: migrating users and sessions off a hosted auth provider later is slow and risky, so check data export and standards support before committing.
What to check before you pick one
- Standards compliance: Look for APIs that support OAuth 2.0 and OpenID Connect for maximum interoperability.
- MFA support: Multi-factor authentication options (TOTP, SMS, email) add critical security layers for sensitive apps.
- SDK availability: Official SDKs for your language or framework significantly reduce integration time.
Frequently Asked Questions
What are authentication APIs?
Authentication APIs provide services for verifying user identity, managing OAuth flows, implementing single sign-on (SSO), and issuing tokens such as JWTs for secure application access.
What is the difference between OAuth and API key authentication?
OAuth is a delegated authorization framework that allows users to grant third-party apps limited access to their accounts without sharing passwords. API keys are simpler static credentials used for server-to-server communication.
Which authentication API should I use for my app?
For most web apps, Auth0 or Okta provide managed identity platforms with free tiers. For simpler needs, a JWT-based solution or social OAuth via Google or GitHub may be sufficient.