1. Swagger Codegen

🔹 Why use it?

• Officially maintained by the OpenAPI Initiative
• Supports multiple languages (C#, Java, TypeScript, Python, etc.)
• Can generate server stubs and client SDKs

🔹 Key Features:
✅ Command-line & UI support
✅ Supports OpenAPI 2.0 & 3.0
✅ Customizable templates

🔹 Best For:

• If you need to generate clients for multiple languages
• If you prefer command-line tools over UI-based solutions

🔹 Get it here:
https://github.com/swagger-api/swagger-codegen

2. OpenAPI Generator

🔹 Why use it?

• A fork of Swagger Codegen with faster updates and better maintainability
• Supports more languages than Swagger Codegen
• Supports C# clients with HttpClient or Refit

🔹 Key Features:
✅ Generates API clients in over 50 languages
✅ Supports Spring Boot, Express, Flask, and more for server-side generation
✅ Command-line and Gradle/Maven integrations

🔹 Best For:

• If you want more frequent updates and community contributions
• If you need advanced C# client options (e.g., Refit, RestSharp, HttpClient)

🔹 Get it here:
https://github.com/OpenAPITools/openapi-generator

3. AutoRest

🔹 Why use it?

• Microsoft’s official tool for generating C# API clients
• Best integration with .NET projects
• Works well with Azure REST APIs

🔹 Key Features:
✅ Generates strongly-typed C# clients
✅ Built-in support for Azure REST APIs
✅ Can be customized with PowerShell and JSON configs

🔹 Best For:

• If you primarily work with .NET & Azure
• If you want official Microsoft support

🔹 Get it here:
https://github.com/Azure/autorest

4. Refit

🔹 Why use it?

• A lightweight, RESTful API client generator for .NET
• Uses C# interfaces instead of generating full-blown client classes
• Works great with Dependency Injection

🔹 Key Features:
✅ Uses attributes to define API endpoints
✅ Works with HttpClient
✅ Minimal boilerplate

🔹 Best For:

• If you prefer a simple, lightweight approach
• If you use ASP.NET Core and DI

🔹 Get it here:
https://github.com/reactiveui/refit

5. Kiota

🔹 Why use it?

• Microsoft’s modern API client generator
• Supports OpenAPI-based APIs
• Works with .NET, TypeScript, Python, Java

🔹 Key Features:
✅ Generates strongly-typed API clients
✅ Works with Microsoft Graph API
✅ Supports multiple programming languages

🔹 Best For:

• If you need Microsoft-backed tools for OpenAPI clients
• If you work with Graph API

🔹 Get it here:
https://github.com/microsoft/kiota

Comparison Table

Which One Should You Choose?

• If you want full OpenAPI client generation in many languages → OpenAPI Generator
• If you work in .NET/Azure → AutoRest
• If you prefer lightweight API clients → Refit
• If you need a Microsoft-backed tool for OpenAPI → Kiota