API Versioning and Deprecation Checklist

When to Use This Checklist

Use this checklist when introducing a new API version or retiring an old one. APIs are contracts, and consumers depend on stability. A disciplined versioning and deprecation process lets you evolve an API while giving clients a clear, monitored path to migrate without surprise breakage.

How to Use This Checklist

First decide whether the change is backward-compatible or breaking, since only breaking changes require a new version. Identify every consumer and their usage so you can communicate directly. Run old and new versions in parallel, publish a migration guide, and announce a firm sunset date. Emit deprecation headers and monitor traffic on the old version so you retire it based on evidence, not assumption. Keep a rollback path until the new version is proven.

What Good Looks Like

Clean versioning means breaking changes are isolated to new versions while compatible changes ship in place. Consumers receive a migration guide, deprecation headers, and a firm sunset date. Both versions run in parallel with contract tests, and traffic on the deprecated version is monitored until it reaches zero. The old version is removed only after migration completes or the sunset date passes, with a documented rollback available throughout.

Common Pitfalls

A frequent mistake is treating a breaking change as compatible, silently breaking clients. Sunsetting without a firm date and reminders leaves consumers unprepared. Retiring the old version while traffic remains causes outages. Skipping contract tests during overlap lets the new version diverge. Finally, missing migration guides and SDK updates push migration cost onto every consumer.

Related Resources

Review the Stripe API versioning policy, API backward compatibility, semantic versioning, contract-driven development, and the expand-and-contract migration pattern.