Open Source Postman Alternatives

Hoppscotch is an open-source API development ecosystem designed for building, testing, and debugging REST, GraphQL, and real-time APIs. It provides a unified platform that functions across web browsers, desktop applications, and command-line interfaces, allowing developers to manage the entire API lifecycle from a single environment. The platform distinguishes itself through a highly interactive, command-driven interface that utilizes a global spotlight palette and keyboard shortcuts to streamline complex workflows. It supports advanced request manipulation and validation by executing JavaScript-based scripts and assertions within a sandboxed runtime. Furthermore, it integrates AI-assisted tools to automate the generation of request payloads, test scripts, and documentation, while maintaining compatibility with existing API definitions and collections from other formats. Beyond core testing capabilities, the project offers a collaborative workspace for teams to organize, share, and synchronize API collections and environment variables. It includes robust support for diverse authorization methods, proxy interception for network requests, and enterprise-grade features such as SCIM user provisioning and activity auditing. The software is available for self-hosted deployment via containerized architectures, ensuring consistent behavior across various production and development environments.

Insomnia is a cross-platform API development environment that integrates a request debugger, schema design tools, a mocking server, and a test automation framework. It provides a unified workspace for sending requests and analyzing responses across REST, GraphQL, gRPC, and WebSocket protocols. The platform enables the design and preview of API specifications through a visual editor and allows for the simulation of backend behavior using mocking tools. It supports organizing and synchronizing API collections via local storage, cloud synchronization, or Git. The suite includes a command-line interface for executing linting and testing tasks within continuous integration pipelines. It also features a plugin system for third-party extensions and a secure system for storing environment variables locally to protect sensitive credentials.

Yaak is a cross-platform desktop client and command-line utility designed for developing, testing, and debugging API endpoints. It supports multi-protocol request execution for REST, GraphQL, and gRPC services, providing a unified environment for managing network interactions, authentication credentials, and automated testing workflows. The tool distinguishes itself through a local-first architecture that stores all workspace configurations and request definitions directly on the filesystem. This design enables native integration with version control systems like Git, allowing teams to track changes to API specifications and share project structures. Furthermore, it utilizes operating system keychains for secure credential management and offers a modular plugin system to extend functionality through custom authentication methods, data importers, and template functions. Beyond manual testing, the platform facilitates complex workflow orchestration by supporting request chaining, dynamic payload generation, and scriptable test suites. These capabilities are exposed through a command-line interface, enabling the integration of automated endpoint validation and connectivity testing directly into continuous integration and deployment pipelines. The system also maintains persistent streaming runtimes to support real-time data flow and bidirectional communication with network services.

Insomnia is a desktop application designed for the design, testing, and debugging of network requests. It serves as a comprehensive environment for managing the API lifecycle, allowing users to draft interface specifications, simulate endpoints, and execute automated testing workflows within continuous integration pipelines. The platform distinguishes itself through a modular, plugin-based architecture that enables the integration of custom scripts and external tools. It supports complex development needs by providing a local-first data persistence model, environment-variable substitution for managing different deployment stages, and request-response interception middleware for real-time validation and authentication. Beyond core request handling, the application facilitates team collaboration by synchronizing configurations and security credentials across environments. It includes tools for managing role-based access and identity, ensuring that sensitive API resources remain organized and secure throughout the development process.

Bruno is a local-first API client designed for building, testing, and managing network requests across a wide range of protocols. By storing all collections and configurations as plain-text files directly on the local filesystem, it enables native version control and offline access, ensuring that project data remains under user control without requiring cloud synchronization. The platform distinguishes itself through a declarative approach to API management, utilizing a domain-specific language to define request parameters and metadata. This architecture supports a robust testing environment where users can execute custom JavaScript-based validation scripts, perform complex assertions, and automate multi-step workflows. Its multi-protocol engine provides a unified interface for interacting with REST, GraphQL, gRPC, WebSocket, and SOAP services, while integrated environment-aware management allows for seamless switching between different deployment configurations. Beyond core request execution, the tool includes a comprehensive suite of utilities for documentation generation, secure authentication, and CI/CD integration. It supports advanced security workflows through various credential management protocols and secret providers, while its command-line interface facilitates parallel execution and data-driven testing within automated pipelines. Users can also leverage AI-driven automation to generate collections and test scripts, further streamlining the development process.

This is a desktop HTTP client application used for constructing, sending, and analyzing HTTP and GraphQL requests. It provides a graphical interface for API development and testing, including a dedicated GraphQL client with schema-driven autocomplete and validation. The project features an integrated AI assistant that generates API requests from natural language prompts. It supports a complex organization system of spaces and collections with hierarchical authentication inheritance and recursive variable resolution for dynamic request values. The tool covers a broad range of capabilities, including response analysis with client-side HTML rendering, multi-format payload management, and cross-platform data synchronization. It includes security controls for SSL validation and local-only secret storage to prevent sensitive data from syncing to the cloud. Additional utility areas include cURL command integration, JSON-based data serialization, and performance monitoring for request timing and size.

Posting is a terminal-based HTTP request manager designed for developing, testing, and documenting API endpoints. It functions as a keyboard-driven interface that allows users to execute requests, manage collections, and inspect server responses directly within the command line environment. By storing request configurations as plain text files on the local filesystem, the tool ensures that API definitions remain compatible with standard version control systems. The project distinguishes itself by treating API collections as version-controlled assets, enabling users to migrate existing workflows from other tools or import standardized API specifications directly into a local workspace. It supports advanced request lifecycle management through user-defined scripts, allowing for dynamic manipulation of headers and payloads. Users can also bridge the gap between terminal commands and structured files by converting between command-line strings and persistent request definitions. The application provides a comprehensive suite of tools for managing complex API environments, including support for environment variable injection, mutual TLS authentication, and SSL verification. The interface is built using modular, reactive widgets that support both keyboard and mouse navigation, supplemented by a centralized command palette for rapid interaction. Users can further tailor their experience through extensive customization options, such as remappable keyboard shortcuts, theme management, and integration with external text editors and pagers.

yapi is an API management platform designed to coordinate the development of RESTful APIs between frontend, backend, and quality assurance teams. It functions as a centralized system for documenting interface specifications, simulating server responses, and validating requests through a built-in testing client. The platform features an API code generator that transforms interface specifications into typed request functions and data models across multiple programming languages. It also includes a mock server capable of generating synthetic responses using schema-based generators and rule-based simulation. The system provides tools for interface documentation, automated API testing with response assertions, and an importer for migrating definitions from formats such as Postman and Swagger. User access to these resources is managed via a flat-hierarchy permission system.

Karate is an end-to-end testing framework and API test automation tool used to validate REST and SOAP APIs, drive browser interactions, and measure system performance. It functions as a unified solution for executing automated tests across both API backends and web frontends. The framework utilizes a custom domain specific language and Gherkin-style feature mapping to define requests and assertions. It includes an API mocking server to simulate backend responses, enabling development and integration testing without live dependencies. The tool covers a broad range of functional testing categories, including browser automation for UI component and workflow verification, as well as load testing to measure service stability under high-volume traffic. These capabilities are integrated into a single engine that handles both network requests and browser sequences.

GraphQL Playground is an interactive development environment and API client used for writing, testing, and debugging GraphQL queries, mutations, and subscriptions. It functions as a visual tool for executing requests against a GraphQL server and inspecting the resulting JSON responses. The project includes a documentation browser for exploring schemas and an editor with autocompletion and error highlighting. It provides specialized capabilities for analyzing API performance through tracing visualization and supports real-time data updates via subscription streaming. The environment allows for switching between multiple API endpoints and project configurations. Users can share specific request states and headers through URL-encoded workspace snapshots to facilitate collaborative API testing. The interface can be embedded directly into a web server using middleware integration.

http-prompt is an interactive HTTP client and API testing CLI designed for constructing and debugging network requests to REST and GraphQL endpoints. It functions as a command-line request builder and a shell extension built on top of HTTPie. The tool provides an interactive shell interface featuring request autocomplete and real-time syntax highlighting for requests and responses. It incorporates stateful session management to maintain request history and session data across multiple commands. The project covers API request automation and REST API debugging, allowing users to send and verify HTTP requests from the terminal.

Swagger UI is an OpenAPI specification renderer and documentation interface that transforms JSON or YAML API definitions into a navigable, searchable website. It functions as an OpenAPI documentation UI and request client, providing a visual catalog for exploring endpoints and sending live HTTP requests to a server using a schema-defined interface. The project distinguishes itself through a plugin-based extension system and a schema-driven UI generation model. This architecture allows for the injection of custom components, state selectors, and helper functions to modify core behavior and layout, as well as the use of a request pipeline to intercept and modify network traffic. The system covers a broad range of capabilities, including OAuth 2.0 authorization management for protected resources, API operation filtering, and deep linking to specific operations via URL fragments. It supports various delivery methods, including static asset distribution, HTML embedding as a React component, and containerized deployment.