Glossary
Feature flag terminology, defined
Clear definitions for the concepts behind feature flags, experimentation, and progressive delivery — with code examples where it helps.
Feature flag terminology is inconsistent across the industry. The same concept goes by feature flag, feature toggle, feature switch, and feature bit depending on the team, the language, and the decade the codebase was started. Layered on top are experimentation concepts — A/B tests, multi-armed bandits, exposure events, statistical significance — that each carry their own vocabulary.
These entries are written for engineers who want a precise definition, not a marketing pitch. Each one covers how the concept works, where the terminology comes from, and what it looks like in code. For hands-on guidance, the guides section goes further with implementation walkthroughs.
What Are Feature Flags?
The complete reference: how feature flags work, the four types (release, experiment, ops, permission), targeting rules, and SDK code examples across multiple languages.
Feature Toggle vs Feature Flag: Is There a Difference?
The terms are used interchangeably by most teams — but the history matters. Learn where each name comes from, which industries prefer which, and which to use in your codebase.
See it in action
Feature flags, A/B testing, and experimentation — free up to 1 million events per month.