Suggest an editImprove this articleRefine the answer for “What does a feature flag do?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)**A feature flag** is a mechanism that lets you **turn a specific piece of functionality on or off in an application without changing code or restarting it**. **Key point:** the code is already deployed to production, but the flag is off, users don't see it until the value is changed.Shown above the full answer for quick recall.Answer (EN)Image**A feature flag** is a mechanism that lets you **turn a specific piece of functionality on or off in an application without changing code or restarting it**. ### Why it's needed: 1. **A gradual feature rollout** You can roll out new functionality to 1% of users first, then 10%, then everyone. 2. **A/B tests** It's easy to split users into groups and show each one its own version of the feature. 3. **A fast switch-off when something breaks** Something broke, the flag gets turned off, the feature disappears. No need to rush a fix out. 4. **Flexible configuration** Features can be enabled by role, geography, time, browser, ID, and so on. 5. **Working in production without a rollout** The code is already deployed to production, but the flag is off. Users don't see it. You change the value, the feature activates. --- **Summary:** a feature flag is like a switch above every feature. Turn it on, it works. Turn it off, it's gone. You control the product in real time.For the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.