API Versioning Best Practices for Long-Lived APIs

API versioning is inevitable. No matter how well you design your initial API, business requirements change, better patterns emerge, and breaking changes become necessary. The question is not whether to version, but how to do it without creating a maintenance nightmare.

The Four Versioning Strategies

URL Path Versioning (/v1/users, /v2/users) is the most common and most visible approach. It is easy to understand, easy to route, and makes version selection explicit in every request. The downside is that it creates a new URL namespace for every version.

Query Parameter Versioning (/users?version=2) keeps URLs clean but makes version selection less obvious. It works well when versions differ in response format rather than resource structure.

Header Versioning (Accept: application/vnd.api+json;version=2) is the most RESTful approach but the least developer-friendly. It is invisible in browser URL bars and harder to test casually.

Content Negotiation uses the Accept header with custom media types. It is elegant but complex, and most developers find it harder to work with than URL versioning.

Our Recommendation

For most APIs, URL path versioning strikes the best balance between clarity and practicality. Couple it with a strict deprecation policy:

1. Announce deprecation at least 6 months before removal
2. Add Sunset and Deprecation headers to responses from deprecated versions
3. Provide automated migration guides and tooling
4. Monitor traffic to deprecated versions and proactively reach out to remaining consumers

The goal is not to avoid versioning — it is to make version transitions painless for your consumers. Invest in migration tooling and clear communication, and your developers will thank you.