Best Free & Open Source Alternatives to Postman

HTTPie is a command-line HTTP client designed to make API testing readable and intuitive. Its simple key-value syntax replaces the dense flag combinations of curl, while built-in JSON support, syntax-highlighted output, and persistent sessions make it a faster way to test REST, GraphQL, and other HTTP APIs. HTTPie is written in Python, available as a standalone binary, and licensed under BSD-3-Clause.

HTTPie Desktop is a cross-platform GUI built on the same foundation, offering a visual request builder, saved environments, cookies, and authentication helpers for users who prefer not to live in a terminal. Together, the CLI and desktop apps cover the full range from quick command-line checks to full collaboration-style API workflows.

HTTPie is a long-standing open-source alternative to Postman, Apidog, Paw, and Thunder Client, with 38k+ stars on GitHub and a stable 3.x release line. It is well-suited for developers, QA engineers, and API integrators who want a lightweight, scriptable HTTP tool that does not require an account or sync to a cloud service.

Hoppscotch is a lightweight, web-based API development and testing platform. It supports HTTP requests across all standard methods, WebSocket, GraphQL, MQTT, and Server-Sent Events, and organises requests into collections and folders for easy reuse. Pre-request scripts, post-request tests, and environment variables allow teams to build repeatable, dynamic testing workflows.

Additional features include code snippet generation for more than ten programming languages, cURL import and export, authentication support for Basic, Bearer, OAuth 2.0, and OIDC, and shareable request URLs. Desktop and CLI versions complement the web app, and a self-hosted option is available for organisations that need to keep API definitions on their own infrastructure.

Hoppscotch is designed for individual developers and development teams who want a fast, open, and privacy-friendly alternative to heavier API clients, with real-time collaboration and role-based access controls for shared workspaces.

Insomnia is an API development and collaboration platform for designing, testing, and debugging APIs across multiple protocols including REST, GraphQL, gRPC, and WebSockets. It provides a clean interface for constructing requests, inspecting responses, and organising work into collections. Tests can be automated and run as part of CI pipelines, and API specifications can be mocked directly within the tool.

Projects can be stored locally, in a Git repository, or in the cloud, giving teams flexibility over how they manage and share API work. Role-based access controls and team workspaces support collaborative development, and AI-powered features assist with commit messages and smart suggestions. Insomnia also supports MCP client integration for AI agent workflows.

Insomnia is suited to API developers at all scales — from individual contributors using the free tier to enterprise teams at organisations like Netflix, PayPal, and Tesla who need a secure, extensible platform for managing complex API landscapes.

Bruno is a Git-native API client for testing REST, GraphQL, and gRPC APIs. Unlike cloud-based alternatives, Bruno stores all collections as plain text files in folders on your local machine, making them version-controllable alongside your source code and shareable through standard Git workflows — without requiring any account or cloud sync.

The client is designed to be lean and developer-focused, with no bloat or mandatory telemetry. Because collections live in your repository, access control and audit trails are handled naturally through your existing Git permissions and history. Bruno also supports scripting for pre- and post-request logic, environment variables, and secret management.

Bruno is an excellent fit for developers and security-conscious teams who want fast, local-first API testing that integrates natively into their existing version control and code review processes.

Scalar is an API development platform centred on the OpenAPI standard, providing integrated tooling for documentation, client testing, SDK generation, and API registry management. Its documentation platform renders beautiful, interactive API references from OpenAPI specs and Markdown files, with GitHub synchronisation to keep docs in step with code changes. The API client is a fully open-source, offline-first alternative to Postman for testing and exploring endpoints.

SDK generation automatically produces type-safe client libraries in TypeScript, Python, Go, PHP, Java, and Ruby from an OpenAPI specification. The API registry centralises versioning and management of OpenAPI documents, JSON schemas, and Spectral rulesets with Git integration, providing a single source of truth for API definitions across an organisation.

Scalar is designed for developers and engineering teams who want their API toolchain built on open standards, with consistent documentation, generated SDKs, and a testable client all derived from the same source specification.

Yaak is designed to let you send and organize requests for multiple API types:

• REST, GraphQL, WebSocket, Server-Sent Events (SSE), and gRPC
• Built using Tauri, Rust, and React
• Lightweight and privacy-friendly — no enforced cloud storage, minimal telemetry, fully offline capable
• Supports importing collections from other tools like Postman and Insomnia
• Offers flexible authentication options: OAuth2, JWT, Basic Auth, and encrypted secrets

🔗 GitHub Repository

💡 Why You Might Like It

• 🧩 All-in-one API tool — handle REST, GraphQL, WebSockets, and gRPC in a single app
• 🔒 Privacy-focused — work locally without cloud lock-in
• 🗂️ Organized workflow — supports workspaces, folders, and environment variables for dev/stage/prod
• 🧠 Git-friendly — stores data in files that can be versioned alongside your code
• ⚡ Modern tech stack — built with Rust + React + Tauri for speed and security

⚠️ Things to Keep in Mind

• Some features are still evolving compared to mature tools like Postman or Insomnia
• Currently has a “bug-fix only” contribution policy (no major new features for now)
• Migrating existing environments may take a bit of setup

Hurl is a command-line tool that lets you run and test HTTP requests using simple plain-text files. Built on top of libcurl, it offers a readable, diff-friendly format for defining requests, assertions, and captures — making it ideal for automated API testing, continuous integration pipelines, and command-line workflows.

Unlike GUI-based API clients, Hurl stores tests as plain text that can be version-controlled, reviewed in pull requests, and executed anywhere without a graphical environment. It supports HTTP headers, query parameters, form data, multipart uploads, cookies, and can capture values from responses to chain requests together.

Hurl is well-suited for developers and DevOps engineers who prefer CLI-first workflows, want reproducible API tests as code, and need a lightweight alternative to heavy GUI clients or complex testing frameworks.

Voiden is a Git-native API client that lets you design, test, and document APIs entirely in plain Markdown. Instead of proprietary collection formats, Voiden uses human-readable API blocks that live alongside your codebase — making collections fully version-controllable, reusable, and diffable through standard Git workflows.

The tool supports REST, GraphQL, and WebSocket APIs, and includes features for composing requests, managing environments, and generating OpenAPI documentation. Being offline-first with no mandatory cloud sync or account requirement, Voiden keeps your API workflows local and private by default.

Voiden is well-suited for developers and teams who prefer Markdown-based documentation, want tight integration between API testing and their documentation pipeline, and value the portability and transparency of plain-text formats over locked-in proprietary clients.