APIs evolve. New features, corrections, deprecations. But clients depend on the current interface. Versioning allows evolution without breaking existing applications. This guide presents strategies and best practices.
Why Version
Compatibility
Old customers continue to work.
Evolution
Improve without blocking.
Documentation
Clarity about what to expect.
Transition
Time for customers to migrate.
When to Version
Breaking Changes
Changes that break contracts.
Examples
- Remove field
- Change data type
- Change meaning
- Remove endpoint
Do Not Version For
Additions, which are generally compatible.
Versioning Strategies
URLPath
/api/v1/users, /api/v2/users.
Query Parameter
/api/users?version=1.
Header
Accept-Version: v1 or API-Version: 2.
Content Negotiation
Accept: application/vnd.myapi.v1+json.
URL Path Versioning
Advantages
Visible, clear, easy to route.
Disadvantages
URLs change with version.
Example
GET /api/v1/products GET /api/v2/products
Common
Most popular approach.
Header Versioning
Advantages
Clean, semantically correct URLs.
Disadvantages
Less visible, harder to test.
Example
GET /api/products Header: API-Version: 2
Semantic Versioning
Format
MAJOR.MINOR.PATCH.
MAJOR
Breaking changes.
MINOR
Compatible additions.
PATCH
Cool bugs.
For APIs
Generally only MAJOR in the public version.
Deprecation
Process
Mark as deprecated before removing.
Communication
Headers, documentation, changelog.
Timeline
Migration deadline.
Support
How long to keep deprecated.
Sunset Headers
HTTPHeader
Sunset: Sat, 01 Jul 2024 00:00:00 GMT.
Deprecation Header
Indicates that it is deprecated.
Communication
Clients can automatically detect.
Migration
Documentation
What changed, how to adapt.
Guides
Migration step by step.
Support
Help during transition.
Timeline
Reasonable deadline.
Backward Compatibility
Objective
New clients, old APIs work.
Additive
Add, don't remove.
Default Values
New fields with defaults.
###Optional
New optional parameters.
Forward Compatibility
Concept
Old customers with new APIs.
Ignore Unknown
Ignore unknown fields.
Graceful Degradation
Work without new features.
Design for Evolution
Extensibility
Think about future changes.
Generic Structures
Extensible objects.
Feature Flags
Do not expose incomplete features.
Contracts
Clearly define what you promise.
Multiple Versions
Maintenance
Cost of maintaining several.
Limits
How many to support simultaneously.
Politics
Set clear rules.
Documentation
By Version
Version-specific docs.
Changelog
What changed between versions.
Migration Guides
How to update.
Deprecation Notices
What will come out.
Tools
OpenAPI/Swagger
Versioned specification.
Postman
Collections by version.
API Gateways
Version routing.
Common Errors
Version Too Much
New version for each change.
Do not version
Breaking change without new version.
Deprecate Fast
Not allowing time for migration.
No Communication
Customers surprised by changes.
SDKs and Clients
Corresponding Versions
SDK v1 for API v1.
Maintenance
Keep SDKs updated.
Communication
Notify about new versions.
Conclusion
API versioning is a long-term discipline. Choose a clear strategy, communicate changes and allow time for migration. The result is APIs that evolve without breaking integrations.
##FAQs
1) Which versioning strategy to use? URL path is most common and recommended for most.
2) When to increase major version? For breaking changes that are not backward compatible.
3) How long to support old version? 6-12 months is common. It depends on customers.
4) Can I make changes without versioning? Additions generally yes. No removals/changes.
5) How to report deprecation? Headers, docs, emails, transition period.
Also read
- GraphQL for Applications: Implementation Guide
- Backend for Applications: Architecture, Technologies and Best Practices
- Microservices in Applications: Distributed Architecture for Mobile
- API For Applications
- API for Applications - Step by Step in Everyday Life
- API for Applications - Step by Step to Scaling