Best open-source alternatives to Postman

Hoppscotch is an open source API development tool aimed at developers who need a lightweight way to test and work with APIs. It provides a web app and desktop apps for sending requests, viewing responses, organizing requests, and working with multiple API styles such as REST, GraphQL, WebSocket, MQTT, and Server-Sent Events. The project also includes collaboration-oriented capabilities such as teams, workspaces, shared collections, environments, and role-based access control. It supports authentication and sync across devices, proxy mode for CORS and blocked APIs, request scripting, tests, and add-ons like a CLI and browser extensions. The README points users to self-hosting documentation for setup and to the main documentation site for full feature details.

Bruno is an API client and IDE designed for exploring, testing, and organizing API requests. It positions itself as an alternative to tools like Postman, with a focus on keeping collections directly in the filesystem rather than in a hosted cloud account. The project is aimed at developers and teams who want a privacy-preserving, local-first workflow. It stores collections as plain text using the Bru format, which makes the content easy to version with Git or other version control systems. The README also highlights that Bruno is offline-only and indicates that cloud sync is not planned, emphasizing data staying on the user's device.

Yaak is a desktop API client aimed at developers who need a fast, private, and offline-first way to interact with APIs. It is positioned as a local tool rather than a cloud service, with the README emphasizing no telemetry and no cloud lock-in. The project is built with Tauri, Rust, and React, suggesting a cross-platform desktop application focused on performance and a lightweight footprint. The application supports a broad set of API workflows, including importing collections from common tools and specifications, issuing requests across several protocols, and inspecting responses with query languages like JSONPath and XPath. It also includes collaboration-oriented organization features such as workspaces, nested folders, environment variables, and filesystem mirroring, while allowing extensibility through plugins, template tags, and custom themes. The README points users to the project documentation and feedback site for further learning and support.

Posting is a terminal user interface HTTP client aimed at developers who prefer working from the command line rather than in graphical tools like Postman or Insomnia. It is designed for keyboard-driven workflows and can be used over SSH, making it suitable for remote administration and terminal-centric development environments. The project stores requests locally in YAML files, which makes them easy to inspect, edit, and version control. It supports practical request-management features such as environments, autocompletion, syntax highlighting, customizable keybindings, themes, and import/export workflows including curl, Postman, and OpenAPI specifications. The README also points users to the project website for the user guide and roadmap.

Firecamp is an API development platform aimed at developers who need a single place to design, test, document, and collaborate on APIs. The README positions it as an open-source Postman alternative with a stronger emphasis on developer experience and team workflows. It supports multiple API protocols and offers dedicated playgrounds for REST, GraphQL, WebSocket, and Socket.IO. The project also emphasizes shared workspaces, collection collaboration, authentication testing, scripting, dynamic variables, and a web platform, making it useful for backend, frontend, and mobile teams working on API-driven systems.

Fusio is a self-hosted API management platform designed to sit between data sources and API consumers. It is aimed at teams that want to expose databases and internal services as managed APIs while handling common concerns such as routing, authentication, documentation, SDK generation, and developer self-service. The project provides a backend application for configuring and operating APIs, plus a flexible app system for adding web-based tools from its marketplace. It supports custom backend logic in PHP or JavaScript, REST API access, and officially supported SDKs across multiple languages, making it suitable both for API builders and for downstream application developers. The README also highlights AI-oriented capabilities such as agent tools and natural-language-assisted development.

Yaade is an open-source API development environment designed for teams that want a self-hosted alternative to tools like Postman. It emphasizes keeping sensitive API data on the user's own server, with collaboration features that let teammates share collections and manage access. The project combines a TypeScript/React/Vite single-page app with a Kotlin backend and a file-based H2 database. Users typically run it in Docker and pair it with a browser extension that proxies requests to handle CORS, while local development can be done with Java, Kotlin, Node.js, and the provided scripts. The README also highlights documentation, scripting, import/export, and request proxying as core workflow features.

WebHook Tester is a self-hosted tool for capturing, inspecting, and debugging webhooks and HTTP requests. It is aimed at developers who need temporary endpoints for testing integrations from services such as GitHub, GitLab, and Bitbucket, or who want an alternative to hosted webhook inspection services. The project runs as a single Go binary with a React-based UI compiled into the executable, so it can be deployed without separate frontend assets. It supports configurable response behavior, real-time webhook notifications over WebSocket, and multiple storage and pub/sub backends, including memory, Redis, and the local filesystem. A tunneling mode based on ngrok can expose a local instance to the internet for receiving external webhook calls.

Request Inbox is a web application for developers who need a simple place to receive, inspect, and manage HTTP requests during testing and debugging. It offers an alternative to services such as webhook.site and is designed around inboxes that can be created, searched, and controlled through a web interface. The project combines a Go backend with a React frontend and exposes a REST API documented with OpenAPI 3.1. It supports authenticated access with GitHub and Google OAuth, private inboxes, API keys, and configurable responses. The README also describes Docker-based deployment, local development workflows, and AWS serverless production infrastructure, suggesting it is meant both for self-hosted use and cloud deployment.