Feature Flag

Used to switch code execution paths based on properties or groupings. Allowing new features to be released, tested and rolled out. Allowing switching back to the older feature quickly if needed. It should be noted that this pattern, can easily introduce code complexity. There is also cause for concern that the old feature that the toggle is eventually going to phase out is never removed, causing redundant code smells and increased maintainability.

Use the Feature Toogle pattern when

• Giving different features to different users.
• Rolling out a new feature incrementally.
• Switching between development and production environments.

• Martin Fowler 29 October 2010 (2010-10-29).