5 Open Source API / REST Development Tools – Postman Alternatives

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Postman is the best API / REST Development tool, unfortunately it is limited to 1000 calls per month. Postman is a great tool but it might not fit everyone that requires unlimited calls. Since it’s a tool for developers you can be sure there are many other similar tools that do stuff a little bit different.

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What are your options? The best alternative for Postman with unlimited calls is none other than open source. Why Open Source? It is more secure because its code is publicly available for review and contributions on GitHub, meaning to say there is no 3rd party harvesting data without your knowledge.

1. SoapUI


In SoapUI, your work is organized into projects, which are displayed under the root node in the workspace navigator. A project can contain any number of functional tests, load tests, and service simulations required for your testing purposes. soapUI is a tool for functional testing, mainly of web services like SOAP based web services and RESTful web services, but also HTTP based services and JMS Services as well as databases.

soapUI is an open source and completely free tool with a commercial companion, soapUI Pro, with extra functionality for companies with mission critical web services. soapUI is being produced by the community as well as the open source company SmartBear. The Most Advanced REST & SOAP Testing Tool in the World. Works on Windows, macOS, and Linux.

  • API Functional Testing – Functionality doesn’t stop at the GUI level. Learn about how to make sure your API functions as intended, every time.
  • API Performance Testing – Performance is the bottom line of your API driven business. Load Test Virtual Users for your API and see how well it performs.
  • API Security – Worried about third party APIs, public APIs, or vulnerable internal APIs? Learn how to safely secure them all.
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2. HTTPie


HTTPie—aitch-tee-tee-pie—is a command line HTTP client with an intuitive UI, JSON support, syntax highlighting, wget-like downloads, plugins, and more. HTTPie is a CLI, cURL-like tool for humans. HTTPie consists of a single http command designed for painless debugging and interaction with HTTP servers, RESTful APIs, and web services:

  • Sensible defaults
  • Expressive and intuitive command syntax
  • Colorized and formatted terminal output
  • Built-in JSON support
  • Persistent sessions
  • Forms and file uploads
  • HTTPS, proxies, and authentication support
  • Support for arbitrary request data and headers
  • Wget-like downloads

3. Advanced REST

Advanced REST

Free and open source API testing tool. Advanced REST client allows you to test your APIs. Easy and clean user interface helps you focus on your API and not tooling. Store your requests and projects on Google Drive and share it with your team. Read documentation for RAML or OAS directly in Advanced REST Client. API console is a world class documentation tool for APIs. It reads the most common API specification languages.

  • Powerful scripting – Make your requests dynamic. Create environments and variables to automate your development. Variables allows you to execute string or mathematical functions. Reduce time when working with repetitive tasks.
  • Request actions and automation – Easly connect to Anypoint Exchange and get yours or others API definition. Use Advanced REST Client as your favourite API documentation tool
  • Advanced Session Management – Advanced REST Client has tools to manage your session via cookies. It allows you to directly create / edit cookies or to use built-in Chrome web browser to log in to external web service.
  • Code snippets – Generate a code snippet from your request and use it when developing a client for your API.
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4. HttpRequester


A tool for easily making HTTP requests (GET/PUT/POST/DELETE), viewing the responses, and keeping a history of transactions. This program is a custom solution to the problem of requiring the use of a HTTP WebApi or similar resource from a language that lacks support for socket communication. The only requirement of the client language is that it has a standard I/O library and is able to execute system commands. You pass a JSON request body to this CLI tool and it will print a response JSON object to the standard out with usual HTTP response information, status, body, request time etc.

5. RESTClient


RESTClient can be used to test a variety of HTTP communications and RESTful web services. Friendly GUI, rich functionalities. RESTClient supports all HTTP methods RFC2616 (HTTP/1.1) and RFC2518 (WebDAV). You can construct a custom HTTP request (custom method with resources URI and HTTP request Body) to directly test requests against a server.

6. StopLight


Best in class API Design, Docs, Mocking, and Testing. Stoplight leverages your OpenAPI documents to drive the entire API development process. Create OpenAPI Specifications (formerly known as Swagger) 10x faster with no specialized knowledge required. Combine OpenAPI documents with Markdown to create beautiful documentation for internal and external stakeholders. Instantly turn any OpenAPI document into a mock server. Leverage contract testing to ensure that your Single Source of Truth – OpenAPI Specification – accurately describes your APIs.


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    A very carefully selected list. You might consider adding ReqBin, an API testing and prototyping tool – Easy, Simple, Efficient. And free.

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    @Anita. ReqBin is an online tool. I’m not used to provide my credentials to an online tool for free.
    Thanks for providing this valuable list with Open Source alternatives.

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