Feature flag

What is a feature flag?

A feature flag, also called a feature toggle, is a way to switch functionality on or off in a running application without deploying new code. The feature lives in the codebase, wrapped in a conditional check against a flag value. That switch decides whether users see it. The point is to separate deploying code from releasing a feature, two acts that traditionally happened at the same moment.

Once that separation exists, control gets precise. Code can sit in production, fully shipped, while the feature stays hidden until it is ready. Then it can go live for everyone, for a subset such as internal testers or five percent of users, or get switched off instantly if something breaks. A team launching a new checkout can route ten percent of traffic to it, watch the numbers, and roll back in seconds without a single redeploy. This is what powers gradual rollouts, A/B testing, and canary releases, and it is standard practice in teams that deploy many times a day.

Flags carry a cost too. Every toggle left in the code after its job is done becomes technical debt, quietly adding branches and complexity. Healthy teams treat flag cleanup as part of the work, not an afterthought, so the codebase does not slowly fill with dead switches.

Feature flags at Dallonses

Flags are how we ship without holding our breath. Putting a new feature behind a toggle means we can release the code, validate it with real traffic, and expand the rollout only when the data backs it up. If something goes wrong, the fix is a switch, not an emergency deploy at midnight.

They fit naturally into our continuous delivery work, where deploying often and releasing carefully are two different decisions. We also set expectations early with clients: a flag has a lifespan, and we retire it once the feature is fully live. That keeps the codebase clean and the release process calm.

Want to release features without betting the whole product on each deploy? Let's wire it up.

Talk to us about safe releases