Openapi3 GitHub Repositories (2026) · Open Source Tools

FastAPI framework, high performance, easy to learn, fast to code, ready for production

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

OpenAPI Generator allows generation of API client libraries (SDK generation), server stubs, documentation and configuration automatically given an OpenAPI Spec (v2, v3)

OpenAPI Diff and Breaking Changes

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

Swagger UI is a collection of HTML, JavaScript, and CSS assets that dynamically generate beautiful documentation from a Swagger-compliant API.

OpenAPI 3.0 and 3.1 and 3.2 (and Swagger v2) implementation for Go (parsing, converting, validation, and more)

OpenAPI based HTTP Client code generator

The open source, cloud native tool for API Mocking and Testing. Microcks is a Cloud Native Computing Foundation incubating project 🚀

Mockoon is the easiest and quickest way to run mock APIs locally. No remote deployment, no account required, open source.

Examples and server integrations for generating the Swagger API Specification, which enables easy access to your REST API

Huma REST/HTTP API Framework for Golang with OpenAPI 3.1

Javascript library to connect to swagger-enabled APIs via browser or nodejs

RapiDoc -WebComponent for OpenAPI Spec

⚒️ Redocly CLI makes OpenAPI easy. Lint/validate to any standard, generate beautiful docs, and more.

vacuum is the worlds fastest and most versatile OpenAPI, Arazzo, AsyncAPI & JSON Schema linter, docs generator and toolkit. It tears through API specs at light speed. 100% compatible with Spectral rulesets, and OpenAPI 3.0, 3.1 and 3.2

Plugin for converting OpenAPI 3.0 specs to the Postman Collection (v2) format

libopenapi is a fully featured, high performance OpenAPI 3.2, 3.1, 3.0, Overlays and Arazzo parser, library, validator and toolkit for go applications.

The most comprehensive collection of quality OpenAPI tooling, curated by Phil Sturgeon and the team at APIs You Won't Hate.

🤖 Generator for GH repo to help you manage the OpenAPI definition lifecycle