What is API Versioning? — UK Software Development Guide

4 min readJune 2025ClickMasters Technical TeamReviewed by James Whitmore, CTO
what is api versioning

Direct Answer

API versioning is the practice of managing changes to an API by maintaining multiple versions simultaneously, allowing existing API consumers to continue using an older version while new consumers adopt the latest version. Common versioning strategies: URL path versioning (/v1/, /v2/), HTTP header versioning (Accept: application/vnd.api+json;version=2), and query parameter versioning (?version=2).

Api-versioning in the UK

API versioning has specific UK government API implications. The GDS API design guide recommends URL path versioning (/v1/, /v2/) for clarity. HMRC Making Tax Digital API uses URL versioning — v1, v2, v3 versions coexist for backward compatibility. UK regulated sector APIs must maintain backward compatibility to avoid breaking dependent systems — breaking changes to FinTech or HealthTech APIs without adequate deprecation notice can create FCA or NHS compliance incidents. ClickMasters implements URL path versioning on all production APIs, with a minimum 12-month deprecation period for removed endpoints.

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