In the early days of software integrations, creating APIs and getting them to work together was a time-consuming and resource-intensive task with a steep learning curve, even for developers.
Fortunately, times have changed. Today, there are dozens of software tools to assist in API design, development, and testing. Some tools specialize in one specific aspect of API development, while others are platforms that can handle most of your needs under one roof.
If you’re looking for the best API design tool for your company, you’ve found the right post. Here, we’ll cover 15 of the best API design software tools on the market today. These tools will help you and your team churn out APIs and updates that meet users’ needs, without requiring you to overhaul your entire process. Let’s get started.
Best API Design Tools
If you’re familiar with REST API design and testing, you may have seen Postman show up on more than one list. Postman is a widely used API platform that can handle everything from design to testing to monitoring. A big reason for its popularity is the intuitive graphical user interface, which helps it stand out from other command-line-based tools.
Heavy on features, Postman is also flexible and customizable enough to adapt to your development team’s needs, no matter your organization’s size or development framework. Its editor allows you to incorporate any special languages or frameworks like GraphQL or OpenAPI.
Postman is cloud-based software that you can access through a Google Chrome extension or a desktop application for Windows, macOS, or Linux. This makes for easier collaboration between remote team members.
What we like: Postman may be the most user-friendly API design tool on the market, allowing team members to more efficiently build and test their applications without a steep learning curve.
Pricing: Postman offers a free version with limited features, as well as paid plans for individual teams ($12/user/month), businesses ($29/user/month), and enterprises ($99/user/month).
SoapUI is an advanced testing tool for REST APIs and SOAP APIs that lets developers test their API security, reliability, and performance with automated testing, mocking, and reporting. It’s popular among software teams and one of the highest-rated tools in its category.
For testing, SoapUI offers both a command-line style interface and a graphical user interface for less experienced testers. Developers may also build libraries of automated tests to more thoroughly and efficiently evaluate their APIs. SoapUI also supports a wide range of API protocols, making it a good fit for almost any team.
SoapUI comes in two versions, the free SoapUI Open Source and the paid ReadyAPI. SoapUI Open Source provides essential testing functionality and can be modified freely by your development team. ReadyAPI offers a broader feature set for building and monitoring automated tests.
What we like: While less accessible than Postman, SoapUI offers a powerful testing solution for REST and SOAP APIs.
Pricing: SoapUI Open Source is free to use. ReadyAPI pricing starts at $759 for a one-year license.
SwaggerHub is another API design platform, made for dev teams building APIs with the OpenAPI specification for RESTful web services. A freemium and open-source product, SwaggerHub includes essential design, testing, and documentation tools to build web services from simple to complex.
In particular, SwaggerHub excels at documentation. API documentation is essential to any functional API, but creating and maintaining docs can often be an afterthought. This leads to out-of-date instructions and frustrated clients.
To help you out, SwaggerHub automatically syncs your API design and documentation as you build the API and offers numerous ways to customize your docs. All of this reduces friction in the build process and ensures your APIs are thoroughly documented.
What we like: SwaggerHub automatically synchronizes your API build and documentation to optimize your workflow and keep docs up to date.
Pricing: The SwaggerHub API editor is free to use for individuals. Team plans start at $75/month. Enterprise solutions are also available.
The Stoplight API platform was created to put high-quality API design at the forefront of development. It empowers developers to rapidly build, maintain, and scale their APIs while keeping their web service efficient, consistent, and reliable for clients.
Stoplight includes tools for API planning, building, mocking, collaboration, and documentation. Like SwaggerHub, Stoplight’s documentation feature creates docs as you configure your API, as long as you conform to OpenAPI standards. Then, share your documentation internally or externally through Stoplight, which hosts your documentation on the cloud.
What we like: Stoplight focuses on consistency and quality and takes a design-first approach to APIs. If you’re having difficulty with quality control, this may be the solution you need.
Pricing: Stoplight offers a free plan, a Starter plan ($79/month), a Professional plan ($319/month), and an Enterprise plan.
If you’re frequently running manual API tests, this one should be in your development toolkit. curl is a command-line tool that lets you send HTTP requests (e.g., GET, POST, PUT, DELETE) from the command line.
With curl, you can run basic tests of your REST API from your terminal without needing to install or pay for fancy software. This will come in handy if you’re doing one-off manual tests. For more extensive and elaborate testing, however, it’s most likely worth the cost to upgrade to a more sophisticated tool.
What we like: curl is a simple HTTP client, a program for sending HTTP requests through your command line on any operating system. Often, sending requests through curl to your API is handy for quick tests and debugging.
Pricing: curl is free to use.
Similar to curl, HTTPie is an HTTP client that works through your command line, allowing you to test your APIs manually. However, you may prefer HTTPie for its intuitive user interface and features more tailored to API testing specifically.
HTTPie is also lightweight to install and use — there’s just one HTTP command which you can add your request content. Plus, the interface is more user-friendly than curl’s, with coloring in its response output and support for file uploads.
Like curl, HTTPie works on Windows, macOS, and Linux operating systems. It also offers a web application and a desktop application if you’d prefer.
What we like: HTTPie is another well-received HTTP client tailored for API testing, instead of HTTP requests in general.
Pricing: HTTPie is free to use.
Here’s one more HTTP request/response tool for you to consider: Hurl is a free program that runs in the command line, and allows you to define your HTTP requests in plain text. You can perform whatever HTTP requests you need to query your API, and the program will capture API responses for you.
Hurl was made to be easy to install and run, and works for any simple REST/SOAP request you need. It also allows for chaining multiple requests at a time.
What we like: Hurl is a simple, fast, reliable HTTP client that you may prefer over curl and HTTPie for testing APIs.
Pricing: Hurl is free to use.
REST Assured is a useful resource for programmers experienced in Java. It’s a free, open-source Java library that makes it easier to automate HTTP requests to REST APIs. Be warned — REST Assured isn’t a platform, and you’ll have to do much of the implementation yourself.
However, in exchange, you have much greater control over your test automation if you go with REST Assured over an API platform.
What we like: REST Assured is a go-to DIY API design solution for many developers, so it’s worth a mention here.
Pricing: REST Assured is free to use.
The Anypoint Platform from MuleSoft is cloud-based software to power your company’s API lifecycle and excels in uniting your company’s services via APIs. The platform lets you quickly build, test, and deploy new applications and make new integrations through a graphical user interface called a composer.
In addition, the Anypoint Platform supports API deployment to cloud services including IBM and AWS, as well as SaaS tools like Box and ServiceNow. And, it offers much of the same functionality as other tools we’ve covered, namely API mocking and documentation. It’s primarily aimed at large businesses and enterprises, so keep that in mind when contacting sales.
What we like: MuleSoft is an industry leader in iPaaS, and its tools make it easy to build integrations with minimal code.
Pricing: Contact sales.
GraphQL is a query language for APIs. it provides API developers with a framework to structure their data and for clients to make requests for that data. If you’re interested in building GraphQL APIs, give Apollo a look.
Used by several major brands, the Apollo platform works to incorporate the GraphQL language across your applications for easier, more streamlined data sharing between new or existing APIs. It implements GraphQL in between your front-end (what users interact with) and back-end (the stored data) to help you handle your data more efficiently than ever.
What we like: Apollo is an enterprise platform dedicated to the popular GraphQL language and a leader in this area.
Pricing: Contact sales.
Many of the tools we’ve mentioned so far include API mocking, in which an API is simulated for testing purposes before the real API goes live. Mocklets is a platform dedicated to API mocking — with it, developers can simulate HTTP-based APIs for testing before pushing their work to production.
Mock APIs built within Mocklets conform to the OpenAPI specification and work like the real thing. Mocklets lets you monitor mock API activity, make quick changes to your mock API for more efficient testing, and ensure your APIs are reliable and secure. It’s also quite cheap compared to other paid products we’ve featured, with plans starting at $5 per user per month.
What we like: Mocklets does one thing very well — it lets you create mock APIs for extensive testing without risking harm to your API.
Pricing: Mocklets offers a free plan, a Premium plan ($5/user/month), and an enterprise solution.
Apiary is all about uniting stakeholders to design the best APIs possible. Owned by Oracle, this platform utilizes the API Blueprint specification for creating APIs. API Blueprint is an alternative API description language that seeks to make collaboration on APIs accessible to everyone by using simpler syntax.
Apiary also comes with handy team administration tools, an interface that shows you which blueprints are in whose hands, automatic documentation generation, and solutions for testing and debugging your Blueprint API.
What we like: Apiary offers a solution for companies who want to work with the API Blueprint language and closely monitor who has control over which assets.
Pricing: Apiary is a feature of Oracle Cloud, which prices based on usage. See the Oracle Cloud pricing page for more information.
Insomnia is our last recommended comprehensive API design platform. It empowers organizations to build effective REST, SOAP, and GraphQL APIs, and is a solid option for non-enterprises. With Insomnia, you can design your APIs around the OpenAPI specification, test your APIs with its built-in API client, manage different environments, and a lot more.
Insomnia also has a clean, modern interface that you can customize to your preference. This way, it’s easy to understand how your API data is organized and identify any problems with it. Insomnia also offers a command-line interface tool for continuous integration and continuous deployment.
What we like: Insomnia presents an affordable solution for smaller companies with essential design features and an approachable interface.
Pricing: Insomnia offers a free plan, an Individual plan ($50/user/year), and a team plan ($120/user/year).
Let’s wrap up this post with a couple of dedicated documentation tools since, as mentioned, good documentation is essential for API adoption. First is Redocly, a tool that builds docs straight from your API definitions.
Redocly treats your documentation like source code by utilizing version control software to track and manage changes. Contributors can go through a review process, so any changes pushed to the documentation must be approved. All interactions are secured, and it's possible to grant different permissions to different writers.
What we like: Redocly applies the same practices of code collaboration to your documentation for easy and efficient documentation tracking and management.
Pricing: Redocly offers a free plan, a Basic plan ($69/month), a Professional plan ($300/month), and an Enterprise solution.
Lastly, we have ReadMe. ReadMe turns your API documentation into interactive hubs for developers, the goal being to tailor your docs to your users.
Users will be able to interact directly with docs by creating their own API calls, then copying and pasting them into their own code. Code snippets are dynamically generated based on your API’s code and updated in real-time when you make changes. ReadMe also supports other resources like feature requests, forums, and changelogs.
What we like: ReadMe lets you create interactive documentation to help your API stand out.
Pricing: ReadMe offers a free plan, a Startup plan ($99/project/month), a Business plan ($399/project/month), and an Enterprise solution.
The Best Software for Designing APIs
A lot goes into a well-designed API, from data structuring to testing to error handling to documentation. Even with the help of software tools, it’s no small undertaking. But it’s also a must for any software company interested in integrations.
Whether you’re looking for a complete platform or a lightweight command-line tool, just about all developers lean on at least one of these tools to get the job done.