In a fast grappling world of systems change, APIs must similarly change but not break the existing clients that utilize them. This is where API versioning comes into play. API Versioning is the technique and mechanisms of managing changes to your application programming interfaces over time. For scalable systems, which likely support thousands to millions of end users, some API versioning mechanisms may help ensure backward compatibility and produce a better experience for developers.
Think about a major new feature that dramatically changes how your API will respond. Without a versioning system in place, the minute you get that change pushed to production, it would immediately affect all your clients regardless of whether or not they were ready for it. If breaking those clients is acceptable then great, you can push your change and break the mobile apps, integrations, or client-side tooling. If you implement proper versioning though, you could progress changes in an incremental fashion without destroying existing consumers.
Often scalable systems have microservices or distributed architectures which allow for different parts of the system to evolve at their own pace. API versioning ultimately becomes a way to manage, track and organize those evolving parts. Whether you’re versioning at the URL level or in a request header or via media types, the common-sense goal is still the same: it should be relatively easy to evolve services without affecting the rest of the system significantly.
Versioning also influences how web development services deliver stable products. Early planning for versioning minimizes the likelihood of rushed remedial action in the later stages. This improves the pace of development and satisfaction of the project team and the customer.
Common API Versioning Strategies
There is no universal solution to versioning, but some practices are more popular than others because they are more obvious and simple. The three most common methods are: URI path versioning, header versioning and media type versioning.
URI Path Versioning
This is arguably the most popular method because of its ease of use. You simply include a version number as part of the URL, for example, /api/v1/products. The developer that is using the API can easily tell what version they are using just by looking at the endpoint.
This method works great for public-facing APIs. It also makes API documentation and tests easier to manage as various versions are clearly delineated. Since everything is explicit, you do not have to worry about something being missed or left out when doing something as simple as documenting a change in the API. But this also means there can be some issues. Over time, this may lead to duplicate code and long and cumbersome routes. It’s becoming extremely difficult to maintain different versions this way unless planned and documented in a clean way.
Despite these disadvantages, URI versioning is still what many RESTful APIs turn to because of its obviousness and friendliness towards developers. I’ve seen this become useful when working with multiple third party teams at the same time.
Header Versioning
Header versioning uses a custom HTTP header to pass the version information, for example, Accept-Version: v2.
This keeps the URL cleaner and affords much better separation of concerns between routing and versioning.
The method is especially useful when addressing internal APIs where the consumers will know how to set headers. It’s similarly useful when following RESTful principals in that there is an emphasis put on stateless communication that minimizes URI length/protocols.
However, it can become less convenient to consume, particularly with testing of APIs among browser and tools like Postman. Additionally, the versioning logic must be part of the API gateway or routing middleware, which introduces extra moving parts to consider.
Nonetheless, header versioning can be a great way to manage API versioning for huge scale enterprise APIs where cleanliness and control come first over simplicity.
Media Type Versioning
With media type versioning (or content negotiation), versioning is built into the Accept header using custom media types like application/vnd.myapi.v2+json. This approach gives you the highest flexibility and is aligned with the notion of hypermedia as the engine of application state (HATEOAS). Media type versioning is especially valuable when you want different representations of the same resource or wanting to support gradual evolution using fine-grained changes.
On the other hand, media type versioning is difficult to implement and understand. Developers often find it unintuitive, which can hinder adoption. Also, documenting and testing are more complex.
Still, for advanced API strategies, media type versioning offers a way to grow and evolve gracefully while maintaining a clean and semantic interface.
Best Practices for Implementing API Versioning
Choosing the right versioning strategy is only part of the picture. To truly benefit from API versioning, you need to follow some key best practices that help your API scale cleanly and effectively over time.
Start Versioning Early
One of the most common mistakes that teams make when it comes to versioning is that they wait to ‘become in need of’ versioning. At that time, it is often too late, and the changes are prohibitive enough that your team often must perform disruptive (but necessary) refactoring. Versioning, as part of your public API, should occur starting from the very first release–you can even call it v1. Establishing this precedent will also give you room to grow.
Beginning to version early allows you to avoid painful transitions as well as makes that particular area of the codebase more manageable for your team. Clients, data consumers, etc… tend to appreciate that the versioning system has been there from the beginning, establishing a level of reliability and repeatability.
Regardless of whether you take a path based approach or header based approach, if you begin to version immediately, you have the best chance of developing an API that can continue to accommodate and meet future needs while still protecting already established integrations.
Deprecate Versions Gracefully
Eventually, you will have to deprecate older API versions. However, deprecating older API versions without warning is a poor way to transition users as it will upset clients and erode trust. The best method to archieve the end goal, is to deprecate gracefully. Be very clear about deprecation timelines and provide client enough time to migrate to the newer version. Provide tooling, migration documentation, or a sandbox environment, so clients can play with the new version. If your users are on a subscription, you might be able to monitor usage patterns for those that are still using deprecated API versions, and serve them targeted notifications.
A strong deprecation policy not only provides an orderly untaxonomy for your systems, but it also provides emphasizes your commitment to a good developer experience and system reliability.
Keep Change Logs and Documentation Up-to-Date
With versioning comes the burden of diligent recording. Each API version should be documented on a new wiki page with the changes, added features and deprecated features documented, in that order.
You can document change logs in detail, but collect the most important details in a human readable format. You have tools at your disposal such as Swagger, Postman and Redoc that help you document by API version. If you’re using your documentation as part of your CI/CD pipeline, even better – you’re documenting in real-time if, and as, code is changed.
Ultimately, documenting is more than just desirable – it is essential. It reduces friction for developers and reduces support tickets. And, importantly, lends to establishing the professionalism and credibility of your API.
How API Gateways and Tools Help in Versioning
It can be overwhelming to manage multiple API versions manually, particularly when your product is growing. You can depend on API gateways, and automation tools to help here. These systems work as traffic directors, allowing you to send requests to the correct API version while being less of a burden on your codebase.
Using API Gateways for Version Routing
Various API gateways such as Kong, Amazon API Gateway, and Apigee have built-in support for version management strategies. They allow you to route based on URI, header, or even request parameters. This way the versioning logic is moved out of your code, making it easier to manage and maintain.
API gateways also allow you to add throttling, rate limiting, authentication, and logging at a single point, allowing your timely application integration to be upgraded without changing your source code. When the gateway supports versioning, updating or removing a version is a simple configuration and not a code change.
This is particularly useful for enterprises and companies managing enterprise web application development. You will have greater scalability, better control, better monitoring or all three! All of which are important when scaling systems.
Leveraging CI/CD for Deployment and Testing
CI/CD pipelines automate largely the process of building, testing, and deploying versions of API. Basically, you can use any CI/CD tools like Jenkins, GitHub Actions, GitLab CI/CD, etc. and each version can be deployed into its own environment or namespace on an orchestrator like Kubernetes.
Automated tests can also be written for your versions so you can be confident changes to one version do not regress another. Versioned deployments also allow you to roll-back or hotfix only the parts of your ecosystem that were affected by the versions you are making modification to.
This is extremely valuable for teams who are transitioning to DevOps or in a fast-moving agile practice – it allows teams to iterate faster without losing trust to be reliable.
Conclusion
API versioning isn’t just a technical requirement, it’s a business advantage. It allows your team to create and innovate without constantly worrying about breaking things and it allows your clients to know that although the system is changing, it is stable and evolving in a thoughtful way.
Start early, pick the versioning strategy that is most appropriate for your audience, and put your time into documentation and automation. Whether you are a startup or building out massive platforms, smart versioning is an essential part of a scalable, future-proof system.
As your API landscape grows, remember the human factor of all this – clear and concise communication, clean documentation and how you approach quality can go a long way in keeping your system and those developing it happy.
And if you’re building or scaling your business online, you should invest in a team that has a clear understanding of APIs and modern systems working in concert with great design – like the people at who also do projects in responsive website design and modern development stacks.