Dark launch

Also called: dark launching

Last updated:

A dark launch deploys a feature into production without releasing it to users. The code is live — running, or ready to run behind a flag at 0% — but invisible. You validate it under real production conditions first, then make it visible when you decide.

Two kinds of dark launch

There are two common flavours. A back-end dark launch runs the new code path without surfacing its results — shadow traffic, dual-writes, or computing a value you discard — to test load and correctness against real data. A hidden-feature dark launch deploys the user-facing feature behind a flag held at off, then flips it on later. Feature flags enable both: the code ships, the exposure is a separate decision.

Dark launch vs progressive rollout

A dark launch is about deploying without releasing — getting code safely into production while it stays invisible. A percentage rollout is about how you then reveal it, expanding from a small cohort to everyone. The two compose: dark launch to land the code, then ramp it up gradually. See the rollout strategies guide for how serving is configured.

Want the full picture? Read the concept guide: Rollout strategies →

Related terms

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.

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.

Feature toggle

Feature toggle is another name for a feature flag — a runtime switch that turns functionality on or off without a code deploy. The terms are interchangeable.

Browse the full feature flag glossary →

Try it in your own app

Free Solo plan covers 10 flags and 2 environments. No credit card, no demo call — sign up and ship.

Get started free See pricing