At Speakeasy, we spend a lot of time working with OpenAPI specs, and we kept running into the same issues: existing parsers are either too rigid, incomplete, or don’t provide the foundations needed to build tools on top of OpenAPI.

So we built our own: speakeasy-api/openapi.

This is a fully open-source library for parsing, validating, and working with OpenAPI specifications. It’s written in Go and designed to be the foundation for SDK generators, documentation tooling, API gateways, and any other infra that needs to deeply understand OpenAPI.

A few things we focused on: • Full Coverage: Handles the entire OpenAPI 3.1 spec (and 3.0.x). • Arazzo Support: Natively parses Arazzo, the new workflow-oriented extension for OpenAPI. • Overlays Support: First-class support for Overlays to make spec customization and composition easier. • Strict Validation: Ensures correctness so downstream tools don’t choke on edge cases. • Composable: Exposes a clean API for building higher-level tooling. • Performance: Optimized for speed and scale.

We open-sourced it because we think the community needs a solid foundation to innovate on top of OpenAPI, especially as the spec evolves with things like Arazzo and Overlays.

You can check out the code here: https://github.com/speakeasy-api/openapi And here’s more detail on the motivation and design in our blog post: https://www.speakeasy.com/blog/release-oss-openapi-library

Would love feedback, contributions, and to hear what you might build with it!