Feature flags and gradual rollouts

A feature flag is a switch that controls whether a new feature is visible. A gradual rollout uses that switch to show the feature to a small share of users first, such as five in a hundred, and then to more of them as it proves stable. For example, a new checkout could be released to a fraction of customers, and switched off straight away if it causes problems, without a new release from developers. Convert Experiences, Optimizely and VWO are examples of tools listed with this feature.

Releasing a change to everyone at once is risky, because a fault affects every customer. Flags let you limit the damage and turn things off quickly. They also let product and marketing teams control launches without waiting for a developer each time. You need them if you have a product with a development team. If you only run a website without product code, you may not need them.

• Can you roll out to a percentage of users and to named groups?
• Can a non-developer switch a flag on or off, and is that change recorded?
• Which languages and platforms do the developer kits support?
• Can you tie a flag to an experiment and measure its effect on a goal?