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Top 23 OpenAPI Open-Source Projects
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Project mention: Mastering Free Autonomous Agents: Self-Hosting Hermes with OpenRouter | dev.to | 2026-09-07
An agent constrained to a local terminal is limited in scope. By enabling the OpenAI-compatible API server, you can integrate Hermes Agent with external interfaces like Open WebUI. To expose your agent to the internet securely, use Pinggy, which allows you to create a secure tunnel to your local endpoint without complex network configuration:
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AppSignal
AppSignal knows why the f*#k it crashed. Stop vibe-debugging. Every exception, every backtrace, grouped so you see patterns, not noise.
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// search("how do I add middleware") {"source_id": "issue_3027", "score": 0.0164, "snippet": "# How to add a header field to the request in a middleware?", "url": "https://github.com/fastapi/fastapi/issues/3027"} // search_code("def jsonable_encoder") {"source_id": "fastapi/encoders.py#jsonable_encoder", "score": 1.0, "snippet": "fastapi/encoders.py jsonable_encoder", "url": "fastapi/encoders.py#L129-L192"} // who_knows("dependency injection") {"author": "sneakers-the-rat", "score": 5.0, "issues": ["issue_13399"]}
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Full disclosure, since you're on Bruno's blog: this is where we tell you about Bruno. We'll keep it factual.
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full-stack-fastapi-template
Full-stack web application template with FastAPI, React, SQLModel, PostgreSQL, Vite, Tailwind CSS, shadcn/ui, FastAPI Cloud, and Docker Compose.
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swagger-ui
Swagger UI is a collection of HTML, JavaScript, and CSS assets that dynamically generate beautiful documentation from a Swagger-compliant API.
Most of the content is the same as what is written here.
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openapi-generator
OpenAPI Generator allows generation of API client libraries (SDK generation), server stubs, documentation and configuration automatically given an OpenAPI Spec (v2, v3)
To be fair I've never used Laravel - but I do have a memory of code generators/scaffolders inserting files that made clear they were responsible for work
/*
* NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
* Do not edit the class manually.
*/
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Kargo
Stop Scripting Promotions. Start Shipping with Kargo. Kargo automates promotion across dev, staging, and prod with approval gates and verification. Open source, built by the team behind Argo CD. Download now.
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gRPC-Gateway reads protobuf service definitions and generates a reverse proxy that translates RESTful JSON HTTP calls into gRPC, based on annotations like google.api.http. (GitHub)
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scalar
Scalar is an open-source API platform:γγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγπ Modern REST API Clientγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγπ Beautiful API Referencesγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγγβ¨ 1st-Class OpenAPI/Swagger Support
Project mention: Build a versioned Laravel API with auto-generated OpenAPI docs in 10 minutes | dev.to | 2026-06-10Open GET /api/doc in a browser. You don't get a raw JSON file β you get a ready-to-use interactive API reference (rendered with Scalar), with a version switcher across v1, v2, β¦ already wired up. The package walked your controllers, read those docblocks, and produced a complete OpenAPI 3.0 document β parameters, enums, response schemas, the lot. These docs can't drift, because they are the code.
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Project mention: Show HN: CLI to order groceries via reverse-engineered REWE API (Haskell) | news.ycombinator.com | 2026-03-29
I just had the best time learning about the REWE (German supermarket chain) API, how they use mTLS and what the workflows are. Also `mitmproxy2swagger`[1] is a great tool to create OpenAPI spec automatically.
And then 2026 feels like the perfect time writing Haskell. The code is handwritten, but whenever I got stuck with the build system or was just not getting the types right, I could fall back to ask AI to unblock me. It was never that smooth before.
Finally the best side projects are the ones you actually use and this one will be used for all my future grocery shopping.
[1]https://github.com/alufers/mitmproxy2swagger
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Project mention: Removing React.js from the codebase and adapting Htmx for UI interactivity | news.ycombinator.com | 2026-07-27
Using Django w/ frontend frameworks has been a struggle for me. (I only dabble as a hobbyist.) I think splitting the backend off into a restful API makes the marriage work. I've looked at django-rest-framework (https://www.django-rest-framework.org/) and django-ninja (https://django-ninja.dev/). Of course,, then you're discarding a lot of batteries that come with the django framework. Perhaps using Django templates for admin / internal facing work only, and React for customer-facing sites can be a healthy compromise?
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API Platform
πΈοΈ Create REST and GraphQL APIs, scaffold Jamstack webapps, stream changes in real-time.
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Project mention: Htmx 4.0, the first JavaScript library to release exclusively on the Game Boy | news.ycombinator.com | 2026-07-26
I don't want to ID my account but they basically look like:
- OpenAPI API spec and using https://github.com/oapi-codegen/oapi-codegen/ to generate the types, server interface, and client library
- Standard library http package for the server implementation
- api served from /api route, htmx webpage served from /
- no ORM, mostly using database/sql for DB transactions, maybe reaching for a query builder library for more complex queries like complex search functionality
- Local S3 compatible object store for dynamic binary data like user-uploaded images and video. Local filesystem can be fine for small scale stuff.
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Project mention: Hyperflask β Full stack Flask and Htmx framework | news.ycombinator.com | 2025-10-16
A lot of people in this thread mentioning the limitations of Flask and βwhy not FastAPIβ etc - but Iβve found Litestar to be the best alternative and it has htmx support out of the box.
https://litestar.dev/
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mockoon
Mockoon is the easiest and quickest way to run mock APIs locally. No remote deployment, no account required, open source.
Project mention: Ψ£Ψ―ΩΨ§Ψͺ CLI Ω Ψ¬Ψ§ΩΩΨ© Ω ΩΨͺΩΨΨ© Ψ§ΩΩ Ψ΅Ψ―Ψ± ΩΩ ΨΨ§ΩΨ§Ψ© Ψ§ΩΩ API | dev.to | 2026-07-10Ψ§ΩΩ Ψ³ΨͺΩΨ―ΨΉ: mockoon/mockoon
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Project mention: How to type third-party API responses in TypeScript (without lying to your compiler) | dev.to | 2026-06-13
REST with an OpenAPI/Swagger spec β openapi-typescript turns the spec into types.
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swagger-core
Examples and server integrations for generating the Swagger API Specification, which enables easy access to your REST API
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Project mention: Why Startups and IndieDevs Should Choose Monolith First, Lessons From My Micro-SaaS Project, For ... | dev.to | 2026-01-09
Type sharing is possible (think NSwag or OpenAPI codegen).
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goa
Design-first Go framework that generates API code, documentation, and clients. Define once in an elegant DSL, deploy as HTTP and gRPC services with zero drift between code and docs.
Anecdotal, but I have built from scratch a fairly large OpenAPI-compliant service using the Goa dsl (https://goa.design) and a coding agent and I've suspected for a while that the reason I've been as productive as I have with few blind alleys is that Goa kept the mistake surface pretty constrained. I also like not having the model generate boilerplate, as Goa's tooling does all that so much more cheaply. YMMV.
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SaaSHub
SaaSHub - Software Alternatives and Reviews. SaaSHub helps you find the best software and product alternatives
NOTE:
The open source projects on this list are ordered by number of github stars.
The number of mentions indicates repo mentiontions in the last 12 Months or
since we started tracking (Dec 2020).
OpenAPI discussion
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Show HN: Open-source control engine for agents
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A note from our sponsor - AppSignal
www.appsignal.com | 13 Sep 2026
Index
What are some of the best open-source OpenAPI projects? This list will help you:
| # | Project | Stars |
|---|---|---|
| 1 | open-webui | 151,481 |
| 2 | fastapi | 102,237 |
| 3 | bruno | 46,916 |
| 4 | full-stack-fastapi-template | 45,519 |
| 5 | OpenAPI-Specification | 31,213 |
| 6 | swagger-ui | 29,004 |
| 7 | openapi-generator | 26,738 |
| 8 | redoc | 25,906 |
| 9 | grpc-gateway | 20,002 |
| 10 | scalar | 16,088 |
| 11 | swag | 13,015 |
| 12 | fastapi_mcp | 12,004 |
| 13 | mitmproxy2swagger | 9,605 |
| 14 | django-ninja | 9,188 |
| 15 | API Platform | 9,184 |
| 16 | oapi-codegen | 8,566 |
| 17 | litestar | 8,455 |
| 18 | mockoon | 8,397 |
| 19 | openapi-typescript | 8,363 |
| 20 | swagger-core | 7,531 |
| 21 | NSwag | 7,365 |
| 22 | goa | 6,100 |
| 23 | springfox | 5,926 |
Sponsored
AppSignal knows why the f*#k it crashed.
Stop vibe-debugging. Every exception, every backtrace, grouped so you see patterns, not noise.
www.appsignal.com