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.