Versioning strategy matters most at the moment you least want to think about it — when you need to ship a breaking change to a field three partners already depend on.
URL versioning (/v1/, /v2/)
Explicit and easy to route, cache, and document. The downside is maintaining parallel code paths for every live version, which tends to calcify into permanent v1 support because nobody wants to coordinate a partner migration.
Header versioning
Cleaner URLs, but versioning becomes invisible in logs and harder to test manually — a real cost when you're debugging a partner integration issue at 11pm.
Additive-only, no versioning
Never remove or repurpose a field, only add new ones. This avoids the versioning problem entirely for a surprisingly long time, until you hit a change that genuinely can't be additive (a field's meaning fundamentally shifting).
What we recommend for most integration-heavy SMEs
Additive-only by default, with URL versioning held in reserve for the rare breaking change — and a deprecation window measured in months, communicated directly to every known consumer before the old path is removed.
Our API Development & Integration team can review your current API surface for versioning risk.