Definition: Configuration mechanism that enables or disables features at runtime without deploying new code, enabling gradual rollouts, A/B testing, and safe deployments.
— Source: NERVICO, Product Development Consultancy
What are Feature Flags
Feature flags (also called feature toggles) are a configuration mechanism that enables or disables application features at runtime, without requiring a new deployment. They function as switches controlling which parts of the code are available to users at any given time.
They are a fundamental tool in modern continuous delivery practices, because they separate code deployment from feature activation.
How they work
The new feature’s code is deployed to production wrapped in a condition that checks a flag’s state. If the flag is off, users continue seeing the previous behavior. When the team decides to activate the feature, they change the flag value without touching code or performing a new deployment.
Flags can be managed with tools like LaunchDarkly, Unleash, or custom configurations. They allow advanced segmentation: activating a feature only for a certain percentage of users, for a specific geographic region, or for internal team members.
Why they matter
Feature flags reduce release risk. If a new feature causes problems, it is deactivated instantly without requiring a rollback. They also enable controlled A/B testing and let product teams experiment with different variants without engineering involvement for each change.
Practical example
A team builds a new search engine for their e-commerce platform. They deploy the code to production with a feature flag turned off. First they activate it only for the internal team for a week. Then they enable it for 5% of users to measure conversion impact. When they confirm it improves sales by 12%, they activate it for everyone. If it had failed, they would have turned it off in seconds.