Even though the philosophy of REST (Representational State Transfer) dominates today’s world of APIs, the older SOAP (Simple Object Access Protocol) is still a force to be reckoned with. SOAP APIs predate much of the growth in APIs we’ve seen in the last decade, reflecting the SOA (Service-Oriented Architecture) evolution that occurred from 2000 through 2008.

Once the iPhone came out, a small-but-vocal group of API believers began espousing the benefits of REST over SOAP, resulting in many enterprises adopting REST for modern mobile and web-centric applications. But if you’re an older and more established enterprise developer, it’s likely you’re still supporting SOAP APIs while also developing the next generation of REST APIs.

SOAP APIs can be public APIs too

It’s a common belief that all public APIs are REST, when in reality there are numerous public SOAP APIs. The RESTful API movement of the last decade just has better storytellers getting the word out through the tech blogosphere, and they’re influencing common beliefs about what a public API is and isn’t. To correct the record a bit, we assembled more than 20 publicly available SOAP APIs into a single Postman Collection so that developers can learn about SOAP APIs while also learning about Postman as a SOAP API client. The public SOAP APIs in this collection complement our existing list of public REST APIs, demonstrating that public APIs can either be SOAP or REST—and that Postman can help you work with APIs across the HTTP spectrum.

Public APIs don’t require authentication and are beginner-friendly

SOAP APIs are enterprise-grade. While REST can reach this level of stability, SOAP is built for it by default. However, like REST APIs, the authentication mechanisms in place for SOAP can vary widely, adding to the complexity of each API being delivered. Authentication is a must for mission-critical API infrastructure, but offering public SOAP API resources makes it easier for developers learning about what APIs are and what they can do. You get to just kick the tires before you commit to actually putting an API to work.

Getting down to business using SOAP APIs

The fact is, SOAP is baked into a significant amount of enterprise software solutions today. And it’s not going anywhere anytime soon. Exhibit A: let’s take a moment to consider the world of electronic data interchange (EDI), which is the backbone of our modern economy. EDI will continue to leverage HTTP in the future, but REST might not always make sense for every EDI scenario.

For example, when it comes to providing self-described, enterprise-grade system integrations, SOAP has clearly defined standards for developers to follow. REST, on the other hand,  is more ambiguous and leaves much open to interpretation—often resulting in more brittle integrations. This opens up new opportunities for SOAP APIs to be deployed. SOAP APIs will remain relevant alongside REST and GraphQL in delivering the API infrastructure behind the business applications we depend on.

Postman is a SOAP client too

We crafted this public SOAP API collection to help underscore what is possible with Postman when it comes to SOAP APIs. Because SOAP uses HTTP just like REST (and even GraphQL), Postman is an effective SOAP API tool. As an API client, Postman provides visibility into the HTTP headers essential to working with most SOAP APIs, while also giving you more control over the body of each API request. This provides you with more options for working with and troubleshooting SOAP APIs.

Check out the Postman Collection of public SOAP APIs and start playing around!