Feature Flag

A switch in the code that turns a feature on or off without a new deployment, letting teams release to some users, run tests, or roll back instantly.

Why it matters

Feature flags let you ship safely and continuously, releasing to a few users first and killing a broken feature in seconds. They are a foundation of modern, low-risk shipping.

For example

The team ships a new checkout behind a feature flag, turns it on for 5 percent of users, and flips it off in seconds when errors spike.

Related terms

A/B Testing Soft Launch Iteration

Go deeper

See how founders actually handle this on Building the product, part of the Starting Up hub.

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