Ory Kratos is an API-first identity and user management system designed for cloud-native applications. It centralizes critical user workflows—login, registration, account recovery, verification, profile management, and multi-factor authentication—so developers don’t have to reimplement them in every service. Built in Go, Kratos scales to billions of users and integrates seamlessly with modern infrastructure like Kubernetes and managed platforms. It’s purpose-built to remove identity logic from application code, offering a standardized, secure, and extensible alternative to proprietary solutions like Auth0 or Okta. Whether you’re a startup prototyping user flows or an enterprise managing global authentication at scale, Kratos provides the foundation without vendor lock-in.
Kratos supports both self-hosted and managed deployment options. The open source version offers the full core engine for development, experimentation, or non-critical workloads. For production use requiring SLAs, enterprise features like SCIM, SAML, organization login (SSO), and CAPTCHA integration, users can adopt the Ory Enterprise License. Integration with Ory Hydra enables full OAuth2 and OpenID Connect compliance, making migration from existing IdPs straightforward.
What You Get
- Self-service identity flows - APIs for login, registration, profile management, and account recovery that can be consumed by any frontend framework via browser or native app flows.
- Multi-factor authentication (MFA) - Support for TOTP, SMS, and passkeys to enforce strong authentication without building custom logic.
- Social sign-in & OIDC integration - Authenticate users via OAuth2 providers like Google, GitHub, or Microsoft without managing credentials directly.
- Identity schemas and traits - Define custom user profiles with JSON Schema, allowing dynamic fields like preferences, roles, or organizational data.
- Admin APIs for lifecycle management - Programmatically create, update, delete, and audit user identities via RESTful endpoints.
- Scalable architecture - Designed for high throughput and low latency, capable of handling 7B+ daily API requests across thousands of companies.
- Ory Hydra compatibility - Works seamlessly with Ory Hydra to provide full OAuth2 and OpenID Connect provider capabilities as a drop-in replacement for Auth0/Okta.
- GDPR-compliant data handling - Built with data locality and user privacy in mind, supporting compliance requirements out of the box.
Common Use Cases
- Building a multi-tenant SaaS dashboard with real-time analytics - Use Kratos to manage user identities across tenants, enforce MFA for admins, and integrate with custom analytics dashboards via identity traits.
- Replacing Auth0 in a high-growth startup - Migrate existing OAuth2/OIDC flows to Ory Kratos + Hydra, reducing costs and gaining full control over user data and authentication logic.
- Problem: Reimplementing login flows in every microservice → Solution: Centralize identity with Kratos APIs - Eliminate duplicated code across services by exposing login, registration, and recovery as a single managed service with standardized error handling.
- DevOps teams managing microservices across multiple cloud providers - Deploy Kratos on Kubernetes in AWS, GCP, or Azure with consistent identity policies and automated scaling based on traffic patterns.
Under The Hood
Ory Kratos is a modular, identity-first authentication service designed to handle complex identity flows with extensibility and developer-friendly tooling at its core. It provides a comprehensive solution for managing user identities, authentication, and authorization in modern applications.
Architecture
The system adopts a well-structured monolithic architecture with clear module boundaries and separation of concerns. It emphasizes service-oriented design principles within a cohesive system.
- Modular organization with distinct responsibilities for identity management, courier services, and configuration handling
- Implementation of strategy and factory design patterns to support flexible authentication mechanisms and message channels
- Use of interfaces and dependency injection to ensure loose coupling between components
Tech Stack
The project is built primarily in Go, leveraging modern frameworks and libraries for robust functionality.
- Built predominantly in Go with integration into web services, configuration management, and database interactions
- Relies on a suite of libraries for HTTP handling, JSON schema validation, OAuth2/JWT authentication, and templating
- Employs Makefiles, Go modules, Docker, and CI/CD tools like goreleaser for streamlined development and deployment
- Features comprehensive test coverage using both Go’s native testing libraries and end-to-end tools such as Cypress and Playwright
Code Quality
The codebase reflects mature testing practices with consistent error handling and maintainable structure.
- Extensive test coverage across core modules, including unit, integration, and end-to-end testing
- Consistent application of error handling patterns with clear propagation and logging mechanisms
- Strong adherence to naming conventions and architectural practices, minimizing technical debt
- Manageable learning curve due to well-defined patterns and modular organization
What Makes It Unique
Ory Kratos distinguishes itself through its identity-centric approach and deep integration within the Ory ecosystem.
- Offers a modular architecture tailored for modern identity management with extensibility baked into core components
- Provides seamless integration with Ory’s broader suite of identity and access management tools
- Supports complex authentication flows while maintaining developer-friendly configuration and tooling