What Is a Feature Toggle?
A feature toggle (or feature flag) is a configuration switch checked at runtime that controls whether a piece of functionality is active, without requiring a new deployment to change it. It lets teams merge and deploy code with a feature hidden, then enable it later, for everyone or a subset of users. This separates deploying code from releasing features.
Why it matters
Toggles let unfinished or risky code ship dark and be enabled gradually, which supports trunk-based development, canary rollouts, and instant rollback by flipping the flag rather than redeploying. The cost is added complexity: stale toggles accumulate and must be cleaned up once a feature is fully launched.
Related concepts
- Decouples code deploy from feature release
- Enables dark launches and gradual rollout
- Stale toggles must be retired to limit complexity
Related guides
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What Is a Dark Launch?A dark launch ships a feature to production turned off or hidden, so it can be tested in the real environment…
What Is a Progressive Rollout?A progressive rollout releases a change to an increasing share of traffic or users in stages, monitoring heal…