APIversioner

APIversioner is a software library and tooling suite designed to help developers manage versioning for application programming interfaces. It provides a centralized mechanism to declare, route, and evolve API versions across services, enabling newer interfaces while preserving compatibility with existing clients.

Core features include version-aware routing that dispatches requests to the appropriate versioned handler based on URL paths (for example /v1/ or /v2/), headers such as API-Version or Accept-Version, or a combination thereof. It supports multiple versioning strategies, a deprecation and sunset policy engine, and automated documentation and client SDK generation. Telemetry tracks usage per version and helps enforce cross-version compatibility.

Architecture comprises a version registry, a routing layer, and adapters for common web frameworks. The version registry stores metadata such as release and deprecation dates, while the routing layer resolves requests to the correct version handler. Adapters exist for frameworks like Express, FastAPI, and Spring, with a language-agnostic core that can be embedded in services written in multiple environments.

Usage typically begins with defining versions and migration plans in a manifest, implementing handlers per version, and configuring the server to enable version negotiation. During deployment, APIversioner can generate client documentation, emit deprecation notices, and integrate with CI/CD pipelines to verify cross-version compatibility.

APIversioner is a conceptual tool aligned with semantic versioning principles. It is positioned as a framework-agnostic approach to API governance and is influenced by common versioning strategies and contract testing practices.