Ory Kratos

Ory Kratos is headless identity management for developers who want auth as an API, not a UI library. It handles registration, login, MFA, account recovery, and profile management through pure API calls — you build the frontend exactly how you want. No opinionated login pages, no UI components you have to style around.

If you're building a custom auth experience and want complete control over every pixel, Kratos gives you the identity backend without the UI opinions. Keycloak is the feature-rich monolith with everything built-in but a steep learning curve. SuperTokens is the developer-friendly middle ground with pre-built UI components. Auth0 is the managed option that gets expensive at scale.

The catch: headless means you build everything. Login forms, error handling, email templates, flow orchestration — it's all on you. Kratos is part of a four-product Ory suite (Hydra, Oathkeeper, Keto) that works together, but deploying and connecting all four is serious DevOps work. For most indie projects, Logto or SuperTokens gets you to launch faster with pre-built UI.