In previous article, we mentioned Open-source Grafana Alternatives but in this article, I have mentioned best and free Postman open source alternatives, which you can try.



SoapUI is the world's most widely-used automated testing tool for SOAP and REST APIs, it is a excellent open source postman alternative.

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.


  • For developers and testers looking to accelerate their ability to deliver REST, SOAP, and GraphQL APIs. SoapUI Open Source is the simplest and easiest way to begin your API testing journey.
  • Automate and fit API testing into your team’s continuous delivery pipeline with the next generation tool built for validation of REST, SOAP, GraphQL, microservices, and other back-end services.
  • Allows API functional testing with Security and Performance testing.
  • Provides API test reports.

Insomnia REST Client


Insomnia REST Client is a powerful REST API Client with cookie management, environment variables, code generation, and authentication for Mac, Window, and Linux.


  • Open Source API Client
  • Design APIs using OpenAPI
  • Automate manual API tests and integrate with your CI/CD process to build out an API testing pipeline using Insomnia Unit Tests and Inso, the Insomnia CLI.
  • Connect directly to Git providers to always be in sync with design changes and enable a GitOps pipeline with Inso, the Insomnia CLI tool.



HTTPie is a command line HTTP client. Its goal is to make CLI interaction with web services as human-friendly as possible. It provides a simple http command that allows for sending arbitrary HTTP requests using a simple and natural syntax, and displays colorized output.

HTTPie can be used for testing, debugging, and generally interacting with HTTP servers.


  • Expressive and intuitive syntax
  • Formatted and colorized terminal output
  • Built-in JSON support
  • Allow Forms and file upload
  • Allows adding Custom Headers
  • You can use Desktop app or terminal.
  • Linux, macOS, Windows, and FreeBSD support

Advanced REST Client (ARC)


ARC is a Cross platform API testing and works on any major platforms including Windows, MacOS and Linux.

Request actions are executed before and after the request. They allows to set variables from request or respose data. Authorization or data processing flows were never been so easy.


  • Open source with Easy and clean user inteface helps you make test request faster.
  • Works with google drive
  • ARC implements it’s own HTTP client that works directly on a socket. As a result you receive detailed information about request timings, redirects and even sent HTTP message body.
  • Unlike other tools, there's no limitations for setting headers with the request or reading headers from the response. You can do more with ARC.
  • ARC as a native application is now more powerful. Use your system variables in the application UI as a regular variable.
  • Read documentation for RAML or OAS directly in Advanced REST Client


Stoplight leverages your OpenAPI documents to drive the entire API development process.

Create OpenAPI Specifications (formerly known as Swagger) very much faster with no specialized knowledge required.


  • Design APIs in Minutes with Stoplight Studio
  • Drive API adoption by providing internal and external developers with always up-to-date interactive documentation , tutorials, and code samples.
  • Allow sharing APIs, tracking changes, managing dependencies, and creating style guides a breeze. 
  • Connect easily with Git providers to always stay on top of project changes.

HTTP Toolkit

HTTP Toolkit is a beautiful, cross-platform & open-source HTTP(S) debugging proxy, analyzer & client, with built-in support for modern tools from Docker to Android to GraphQL.


  • Automatic setup for targeted interception of HTTP & HTTPS from most clients, including:Desktop browsers like Chrome, Edge & Firefox, Android applications and browsers, Backend & scripting languages, like Node.js, Python, Java & Ruby
  • Explore, search & examine HTTP
  • Step through HTTP traffic request by request, or manually mock endpoints and errors.
  • Inject request timeouts, simulate connection failures, and silently redirect requests from one server to another (PRO feature)
  • Create rules to match requests and respond with your own content, to quickly prototype against new endpoints or services. (PRO feature)

That's it, these were some of the best open source Postman alternatives.

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