Application programming interfaces (APIs) are an integral part of modern software applications. APIs allow different software components to communicate with each other by calling different functions and methods. As APIs evolve over time, companies need to decide whether to version their APIs or not. API versioning has some benefits but also some drawbacks that need to be considered.
What is API Versioning?
API versioning refers to the practice of assigning unique version numbers or identifiers to different iterations of an API. For example, a company might release its initial API as version 1.0. Later on, when they add new features or modify existing functionality, they can release this new API as version 2.0. Some common versioning strategies include:
- Incrementing a number, like v1, v2, v3
- Using dates, like 2019-10-01
- Semantic versioning with MAJOR.MINOR.PATCH, like 2.1.5
When an API is versioned, the developer can specify which version they want to target. The version number is usually included in the API request URL. For example:
https://api.example.com/v1/users
https://api.example.com/v2/users
Versioning allows changes to be made to the API without impacting existing consumers. For example, renaming or removing methods won’t break clients that rely on the old version.
Benefits of API Versioning
Here are some potential benefits of releasing versioned APIs:
Backwards Compatibility
One of the main reasons to use API versioning is to maintain backwards compatibility when making updates. Without versioning, even a small change risks breaking existing client applications that rely on the API. With versioning, you can introduce changes under a new version without disrupting apps using the old version.
Clear Separation of Versions
Versioning provides a clean separation between API iterations. Developers can easily understand which version has which functionality and test accordingly. For example, listing API versions on the developer portal helps clarify what changed between each release.
Simplifies Rollbacks
If a bug is introduced in a new API version, rolling back the API is much simpler with versioning. You can rollback to the previous major version without worrying about backwards compatibility issues.
Supports Deprecation Strategies
Versioning allows developers to properly deprecate older API versions. Deprecated APIs can be shut down on a timed schedule without suddenly breaking dependent applications. Developers are given ample warning to migrate to newer API versions.
Adoption Flexibility for Clients
API consumers can choose if and when to migrate to new versions. Versioning gives client applications more control over their own release cycles. They aren’t forced to immediately adopt new versions as soon as they are published.
Drawbacks of API Versioning
Despite the benefits, API versioning also carries some downsides:
More Work Maintaining Multiple Versions
Supporting multiple API versions in parallel creates more work. Developers have to maintain and support legacy versions for as long as clients keep using them. Bug fixes and patches may need to be applied across multiple versions.
Code Duplication Between Versions
There can be code duplication across versions, especially if supporting completely separate codebases for each version. Duplication inflates the size of the codebase and increases complexity.
Confusion Identifying the Right Version
With many versions in play, developers may find it confusing to identify the appropriate version to use. Proper documentation is necessary to outline differences and help users select the correct API version.
Higher Resource Usage
Running different versions in parallel consumes more server resources. Computing resources, storage, and bandwidth requirements all increase.
Fragmented Clients and Ecosystem
Supporting too many API versions fragments your consumers. Some cling to old versions while others move forward, complicating community support and ecosystem unification.
Best Practices for API Versioning
If you do decide API versioning is right for your project, here are some best practices to follow:
Use Semantic Versioning
Semantic version numbers like MAJOR.MINOR.PATCH make differences easy to understand. MAJOR versions for breaking changes, MINOR for new features, and PATCH for bug fixes.
Group Related Changes into Versions
Avoid a new version for every tiny change. Group related updates into milestone releases to limit versioning.
Provide Clear Documentation
Document what is changed, added, and deprecated with each release. Make it easy for developers to stay up to date.
Support Deprecated Versions Temporarily
When deprecating versions, don’t shut them off immediately. Support them for a grace period to give clients time to update.
Monitor Usage and Retire Unsupported Versions
Watch version usage numbers and consistently retire versions with low adoption to limit maintenance.
Offer Converter Utilities
Provide utilities to help users convert between versions or migrate to newer versions.
Use API Gateways
API gateways abstract version differences behind the scenes while routing requests to the correct backend version.
When is API Versioning Appropriate?
Weighing the pros and cons, API versioning tends to work best when:
- Making disruptive changes that break backwards compatibility
- Releasing major updates like new features or significant rewrites
- Deprecating endpoints or functionality
- Changes would negatively impact API consumers
- API has a large or diverse consumer base
For more incremental additions and changes, services may be better served avoiding versions entirely.
Alternatives to API Versioning
Here are some alternative strategies to consider instead of strict API versioning:
Documentation Only Changes
For minor additive changes, document the updates while keeping the existing API untouched. Clients can opt-in to new features at their discretion without impacting compatibility.
Optional Query Parameters
Introduce new optional query parameters for additional functionality while keeping required params the same. Existing calls work as-is.
Optional Request Headers
Similar to query params, optional request headers can toggle functionality in the API. Defaults mirror existing behavior.
Resources Oriented Design
Model API resources more granularly. Make additive changes by adding new related resources under a versioned root.
Media Type Versioning
Version the request/response media type or content. The underlying API remains the same but alternative formats are available.
Endpoint Extensions
Extend API endpoints with additional paths to represent new features, like /v1/users/verified.
Conclusion
API versioning can make managing changes easier when done thoughtfully. But leaning too heavily on versions risks increased complexity, maintenance costs, and fragmentation. Evaluate your own APIs maturity, client needs, and release cadence to decide if strict versioning is appropriate. Where possible, try to offer flexibility and backwards compatibility without versions.