Feature Flag
Toggle that controls feature availability without deploying new code.
Definition
A feature flag (or feature toggle) is a technique that allows teams to enable or disable features in production without deploying new code. This enables safer releases, gradual rollouts, A/B testing, and quick rollbacks when issues arise.
Feature flags decouple deployment from release, allowing code to be deployed continuously while feature availability is controlled separately. This is a core practice in modern continuous delivery and enables more experimental, iterative development.
Why It Matters
Feature flags reduce deployment risk and enable faster iteration by separating code deployment from feature launch. Understanding this practice helps teams ship more confidently and experiment more freely.
For product teams, feature flags enable testing with real users before full rollout, reducing the cost of failed experiments.
Examples in Practice
A team deploys a new checkout flow behind a feature flag, gradually rolling it out to 1% then 10% then 50% of users while monitoring metrics.
When a bug is discovered in a new feature, the team instantly disables it via feature flag while working on a fix.
A company uses feature flags to run A/B tests directly in production, measuring real user behavior rather than relying on research.