12factor.net — The Twelve-Factor App

A methodology for building software-as-a-service apps published by Adam Wiggins and the Heroku team at https://12factor.net/.

Summary

The twelve-factor methodology was distilled from experience operating and deploying millions of apps on the Heroku platform. It describes twelve principles for building cloud-native, horizontally scalable, deployable applications.

Key Takeaways

1. Codebase — One codebase, many deploys; shared code via dependency managers, not shared repos.
2. Dependencies — Explicitly declare all dependencies; no implicit system-level packages.
3. Config — Store config in environment variables; never in code or named environment groups.
4. Backing Services — Local and remote services are interchangeable attached resources.
5. Build, Release, Run — Three separate, immutable stages; releases are versioned.
6. Processes — Stateless, share-nothing processes; all persistence via backing services.
7. Port Binding — App is self-contained, binds its own port.
8. Concurrency — Scale by adding stateless processes, not by threading.
9. Disposability — Fast startup, graceful shutdown; crash-resilient.
10. Dev/Prod Parity — Minimize time, personnel, and tools gaps between environments.
11. Logs — Write to stdout; let the platform route and store.
12. Admin Processes — Run as one-off processes in the same environment as the app.

Wiki Pages That Cite This Source

• Twelve-Factor App — full treatment of all 12 factors
• Continuous Integration and Delivery — Factor V (Build/Release/Run)
• Infrastructure as Code — Factor IV and Factor X
• Blue-Green Deployment — Factor IX (Disposability)
• Canary Release — Factor V (immutable releases)