Kill switch

Also called: ops toggle

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A kill switch is a feature flag whose job is to switch a feature off fast. When something goes wrong in production, you set the flag to off and every connected SDK serves the fallback on its next evaluation — within seconds, with no deployment, rebuild, or rollback.

When you reach for a kill switch

Common triggers: a third-party dependency starts timing out, a new feature spikes database load, or a bug surfaces only under production traffic. Wrapping risky or resource-heavy behaviour in a flag means the mitigation is a single switch rather than an incident-length revert. Teams often pair a kill switch with a percentage rollout so they can both ramp exposure up and cut it to zero instantly.

Kill switch vs rollback

A rollback reverts a deployment: it is slower (rebuild and redeploy), coarse (it reverts everything in that release, not just the broken feature), and risky during an incident. A kill switch is scoped to one feature and takes effect on the next flag evaluation. The new code stays in the binary — no traffic executes it — so you can triage the root cause without the clock running.

Want the full picture? Read the concept guide: What are feature flags? →

Related terms

Feature flag

A feature flag is a conditional in your code whose value is controlled from a remote dashboard, letting you turn functionality on or off without deploying new code.

Percentage rollout

A percentage rollout serves a feature to a defined share of users — chosen by a deterministic hash — so the same users stay in the cohort as you ramp the percentage up.

Dark launch

A dark launch ships a feature to production turned off or invisible to users, so the code runs in the live environment before anyone sees it — you reveal it later on your own schedule.

Browse the full feature flag glossary →

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