LaunchDarkly Developer Documentation

Get started in under 30 minutes.
LaunchDarkly provides feature flags as a service for Java · Python · Ruby · Go · Node.js · PHP · .NET. Control feature launches -- who sees what and when -- without multiple code deploys. Easy dashboard for phased rollouts, targeting and segmenting.
Need more help? write us at

Get Started    Guides

The kill switch

You can use the kill switch to turn off a feature that's misbehaving without needing to touch any code or re-deploy your application.

The kill switch is available on both the LaunchDarkly dashboard and the Targeting tab.

When you toggle the kill switch to "off", you are turning off the targeting rules for that flag and serving the "off" variation.

In the Targeting tab, you can choose the "off" variation for both boolean and multivariate flags. For boolean feature flags, we'll default to serving false when the feature flag has been killed.

If there's no setting for the off variation, we'll serve the fallback (or default) value specified in your code's variation calls. The LaunchDarkly UI also shows this variation once we start receiving requests for your feature flag.