Open Source #API Projects

Open source API development ecosystem - https://hoppscotch.io (open-source alternative to Postman, Insomnia)

Open-source command-line and desktop HTTP client with intuitive syntax, JSON support, and built-in auth — a developer-friendly Postman alternative.

Scalar is an open-source API platform:　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　🌐 Modern Rest API Client　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　📖 Beautiful API References　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　✨ 1st-Class OpenAPI/Swagger Support

Opensource IDE For Exploring and Testing API's (lightweight alternative to Postman/Insomnia)

An open-source, single-executable Firebase alternative with sub-millisecond REST and realtime APIs, built-in auth, a WebAssembly runtime, and an admin UI.

Run and test HTTP requests with plain text — a simple yet powerful command-line tool for API testing.

The open-source, cross-platform API client for GraphQL, REST, WebSockets, SSE and gRPC. With Cloud, Local and Git storage.

A fully open-source headless CMS with Git support, Markdown editing, and live visual preview for React-based sites.

Open-source, TypeScript-first headless CMS and app framework that runs natively in Next.js with a code-defined backend and admin UI.

Open source AI gateway and router that exposes hosted, BYOK, local, and custom models through one OpenAI-compatible API.

Local-first desktop API client for REST, GraphQL, gRPC, WebSocket, and SSE — Git-friendly collections, a CLI, and no cloud lock-in.

Fast, typo-tolerant open-source search engine with vector, hybrid and semantic search — a simpler, cheaper alternative to Algolia.

Open-source no-code platform for web scraping, crawling, monitoring and AI data extraction.

Open platform for governing execution authority at decision surfaces across agents, AI systems, and enterprise workflows.

Source-available headless CMS and backend that turns any SQL database into REST and GraphQL APIs with a no-code admin Studio.

Design, test and document APIs in plain Markdown with a git-native, offline-first approach.

Bitwarden infrastructure/backend (API, database, Docker, etc).

An open-source, code-first CRM you can customize, version, and self-host — an alternative to Salesforce and HubSpot.

Open-source managed agent platform for running AI agents on any model and any machine, self-hostable via Docker.