Why Version Your API — Breaking vs Non-Breaking Changes

In this tutorial, you will learn about Why Version Your API. We cover key concepts, practical examples, and best practices to help you master this topic.

Understanding the difference between breaking and non-breaking changes determines when a new API version is required to protect existing clients from unexpected failures.

Non-Breaking Changes

Adding new endpoints, adding optional response fields, adding optional request parameters, relaxing validation rules, and increasing rate limits are non-breaking.

Breaking Changes

Removing endpoints, removing or renaming fields, changing field types, making optional fields required, changing URLs, and changing authentication requirements are breaking.

Decision Flow

Use a decision checklist for every change. If any breaking change is identified, a new version is required. Document the decision in a change log.

Common Mistakes

1. Assuming additive changes are always safe — Adding required response fields can break clients.
2. Not communicating upcoming breaking changes — Give advance notice.
3. No versioning policy — Each team decides individually.

Practice Questions

1. What are three examples of non-breaking changes?
2. What are three examples of breaking changes?
3. Why might an additive change be breaking?

What's Next

In the next lesson, you will learn URI versioning.