Openapi3 GitHub Repositories (2026) · Open Source Tools

😎 A list of awesome projects related to OpenAPI 3.0.x, curated by the community

Shift-left API Integration | Auto-fix integration drift before integration. Specmatic turns API specifications into executable contracts, continuously verifying that every change made by AI coding agents and engineers stays true to the desired behaviour. Ship AI-ready APIs 10x faster, from intent to implementation, with Spec-Driven API Development.

Generate VitePress API Docs from OpenAPI specifications

A plugin for the Fastify webserver to autogenerate a Fastify configuration based on a OpenApi(v2/v3) specification.

Generates OpenAPI document from OData CSDL

Self-hosted execution layer for AI agents: connect any agent to real APIs, scope exactly what it can touch, and keep credentials out of the agent's hands.

A RESTful framework built on top of light-4j with both Swagger 2.0 and OpenAPI 3.0 supports

Detect breaking changes between OpenAPI 3.0/3.1 specs. Explainable Web UI, CLI and CI gate; local-first and deterministic, with optional AI summaries.

Open-source OpenAPI mock server with cloud hosting and local modes for development, testing, and CI. Generates realistic API responses from specs with latency simulation, error injection, proxy fallback, and request validation. Validated against 2,200+ real-world OpenAPI specs.

The OpenAPI v3 specification for DigitalOcean's public API.

openapi_first is a Ruby gem for request / response validation and contract-testing against an OpenAPI API description. It makes APIFirst easy and reliable.

Generates Kotlin Code from OpenAPI 3 Specifications

Generate Refit interfaces and contracts from OpenAPI (Swagger) specifications

A fast Java JSON schema validator that supports draft V4, V6, V7, V2019-09 and V2020-12

A fast serialization and validation library, with builtin support for JSON, MessagePack, YAML, and TOML