vocabulary: provider: Unleash description: >- Domain vocabulary for Unleash, the open-source feature management platform. Covers feature flags, activation strategies, environments, projects, targeting segments, variants, metrics, and access control concepts. version: '2026-05-03' tags: - Feature Flags - Feature Management - Progressive Delivery - Experimentation terms: - term: Feature Flag definition: >- A conditional toggle in code that enables or disables a feature without deploying new code. Also called a feature toggle or feature switch. Unleash feature flags are named identifiers with per-environment enablement states and activation strategies. tags: - Core Concept - term: Feature Toggle definition: >- Synonym for Feature Flag. A mechanism to turn features on or off at runtime without code deployment, enabling trunk-based development, A/B testing, canary releases, and kill switches. tags: - Core Concept - term: Project definition: >- A logical grouping of feature flags in Unleash. Projects have their own set of environments, members, and access controls. The default project is named "default". tags: - Organization - term: Environment definition: >- A deployment target context (e.g. development, staging, production) where feature flags can be independently enabled or disabled. Flags may be on in development but off in production until a release is ready. tags: - Infrastructure - term: Activation Strategy definition: >- A rule defining when a feature flag is considered enabled for a given request context. Strategies include gradual rollout (by percentage), user ID lists, IP addresses, hostnames, and custom strategies. tags: - Targeting - term: Gradual Rollout definition: >- A built-in Unleash strategy that enables a flag for a configurable percentage of users or sessions, using sticky hashing to ensure consistent evaluation for the same user. Enables canary releases and progressive delivery. tags: - Targeting - Strategy - term: Segment definition: >- A reusable group of constraints that can be applied to multiple strategies. Segments allow common targeting rules (e.g., "beta users", "enterprise customers") to be defined once and reused across many flags. tags: - Targeting - Reusability - term: Constraint definition: >- A condition on an Unleash context field that limits when a strategy applies. Constraints can check context values using operators like IN, NOT_IN, STR_CONTAINS, NUM_GTE, DATE_BEFORE, etc. tags: - Targeting - term: Unleash Context definition: >- The set of attributes describing the current request or user that Unleash uses for flag evaluation. Standard fields include userId, sessionId, remoteAddress, and environment. Custom properties can also be added. tags: - Evaluation - term: Variant definition: >- A named value returned by a feature flag for A/B testing or multivariate experiments. Variants have a weight (percentage allocation), optional payload (string, JSON, CSV), and override rules for specific users. tags: - Experimentation - term: Impression Data definition: >- An Unleash flag setting that emits events every time the flag is evaluated. Useful for tracking exposure in experiments and for compliance/audit purposes. tags: - Analytics - Observability - term: Kill Switch definition: >- A feature flag of type "kill-switch" designed to rapidly disable a problematic feature in production without a code deployment. Distinct from release flags in that it is expected to remain permanently in the codebase. tags: - Operations - Safety - term: Release Flag definition: >- A short-lived feature flag (type "release") used to control the rollout of a new feature. Once fully released and the old code path is removed, the flag should be archived. tags: - Release Management - term: Experiment Flag definition: >- A feature flag of type "experiment" used for A/B testing and hypothesis validation. Paired with variants to deliver different experiences to user segments. tags: - Experimentation - term: Client API definition: >- The Unleash API endpoint (/api/client) consumed by backend SDKs to fetch complete flag configurations. Returns all flags and their strategies for local evaluation, enabling zero-latency flag checks. tags: - API - SDK - term: Frontend API definition: >- The Unleash API endpoint (/api/frontend) consumed by client-side SDKs. Returns only the evaluated state of flags (enabled/disabled) for a specific context, without exposing strategies or configuration details. tags: - API - SDK - term: Admin API definition: >- The Unleash REST API (/api/admin) providing full programmatic control over flags, projects, environments, users, tokens, and configuration. Powers the Unleash Admin UI and automation integrations. tags: - API - Administration - term: Backend Token definition: >- An API token for server-side SDKs scoped to specific projects and environments. Must be kept secret. Used with the Client API to fetch flag configurations. tags: - Authentication - Security - term: Frontend Token definition: >- An API token for client-side SDKs that is safe to expose in browser/mobile code. Limited to the Frontend API — cannot access admin operations. tags: - Authentication - Security - term: Personal Access Token (PAT) definition: >- A user-specific API token for manually testing or debugging Unleash integrations. Inherits the permissions of the creating user account. tags: - Authentication - term: Service Account Token definition: >- The recommended token type for automation, CI/CD, and integration workflows. Service accounts can have specific RBAC roles assigned independent of human users. tags: - Authentication - Automation - term: Change Request definition: >- An Unleash workflow feature (Enterprise/Pro) that requires changes to flag configurations in production environments to be reviewed and approved before applying, similar to a pull request for feature flags. tags: - Governance - Enterprise - term: Stale Flag definition: >- A feature flag that has been active beyond its expected lifetime and should be cleaned up from the codebase. Unleash can automatically mark flags as stale based on configurable age thresholds. tags: - Technical Debt - term: Unleash Edge definition: >- Unleash's high-performance edge proxy (replacing Unleash Proxy) that sits between client SDKs and the Unleash server to minimize latency, reduce load, and support offline operation. tags: - Infrastructure - Performance - term: SDK definition: >- A language-specific client library for evaluating Unleash feature flags. Official SDKs are available for Node.js, Java, .NET, Python, Go, Ruby, PHP, iOS (Swift), Android (Kotlin), and React. tags: - Integration - SDK