Clearly list every extra piece of software your app needs to work. This makes it easy for the app to be set up on a new computer without missing any parts.

Required Tool List

Store secret passwords and site addresses outside of the code. This allows you to change how the app behaves in different situations without rewriting the code itself.

Separate App Settings

Treat external tools like databases as removable parts that can be swapped out. This way, the app can connect to different services just by changing an address.

Plug and Play Resources

Strictly separate the stages of preparing, packaging, and actually running your app. This process ensures that once a version is ready to go, it cannot be changed accidentally.

The Three Step Launch

The app should work like a factory worker who doesn't remember the previous customer. Any important information should be saved in a separate storage area rather than inside the app itself.

Memory Free Operations

The app should be able to share its services directly using its own unique digital address. This removes the need for extra software to manage how users find the app.

Self Contained Address

To handle more users, simply run many identical copies of the app at the same time. This is like opening more checkout lanes at a grocery store to move the line faster.

Scaling with Copies

Make sure the app can start up instantly and shut down safely at any moment. This makes the system more reliable and easier to update without causing problems for users.

Fast Start and Stop

Keep your personal work computer as similar as possible to the real-world server where the app lives. This prevents 'it works on my machine' bugs where the app breaks only when it goes live.

Identical Setup Everywhere

The app should continuously output a stream of notes about what it is doing. This diary helps people monitor the app's health and find the cause of any errors.

The Activity Diary

Run special maintenance jobs, like fixing a database, using the same code and settings as the main app. This ensures that even one-off tasks follow the same rules as the rest of the project.

12-Factor App Methodology Concepts