REST API Versioning Strategies

APIs need to evolve without breaking existing clients. Choosing the wrong versioning strategy leads to maintenance nightmares or forces all clients to update simultaneously.

Three main versioning approaches:

1. URL path versioning (most common)

GET /api/v1/users
GET /api/v2/users

Pros: Clear, easy to route, easy to document
Cons: Duplicates controllers/routes

2. Header versioning

GET /api/users
Accept: application/vnd.myapp.v2+json
# Or custom header:
X-API-Version: 2

Pros: Clean URLs, resource-oriented
Cons: Harder to test in browser, less discoverable

3. Query parameter versioning

GET /api/users?version=2

Pros: Easy to test, optional (default to latest)
Cons: Pollutes query string, caching complications

Best practices regardless of strategy:

• Version the API, not individual endpoints
• Support at least N-1 (current + previous version)
• Use sunset headers: Sunset: Sat, 01 Mar 2025 00:00:00 GMT
• Document breaking vs non-breaking changes
• Non-breaking changes don't need new version:

- Adding fields to responses
- Adding optional request parameters
- Adding new endpoints

• Breaking changes need new version:

- Removing or renaming fields
- Changing field types
- Changing validation rules
- Removing endpoints

API versioning is about managing change. Good versioning lets you evolve the API while giving clients time to migrate. Bad versioning either breaks clients or prevents API evolution.

Designing evolvable REST APIs