Best Free & Open Source Alternatives to SwaggerHub

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.