Definition
API versioning is the practice of managing changes to an APIApplication Programming Interface - standardised interface that allows two systems to communicate with each other. so that existing clients are not broken when the API is updated. Common strategies include URL versioning (/v1/supplier-switch, /v2/supplier-switch), header versioning (Accept: application/vnd.api+json;version=2), or parameter-based versioning. Semantic Versioning (semver) is the standard for communicating the severity of changes: MAJOR (breaking change), MINOR (new functionality, backwards-compatible), PATCH (bug fix). For APIs in the energy sector, versioning is critical: an electricity supplierCompany that sells electricity to end users - purchases power in the wholesale market and sells it to consumers. with an ElhubNational hub for metering data and market processes in the Norwegian electricity market. integration cannot upgrade its API for all customers simultaneously. Deprecation cycles (announcement → transition period → removal) are good practice. Lack of versioning is one of the most common sources of production errors in integration projects.