Open-source alternatives to Springdoc Openapi

swagger-core is a set of libraries for parsing, generating, and serializing OpenAPI specifications to automate REST API documentation. It provides tools to read, validate, and transform JSON or YAML specifications into programmable objects, as well as a generator that scans source code and annotations to create formal technical descriptions of an API. The project enables bi-directional specification serialization, allowing in-memory API definitions to be converted between native language objects and structured files. It uses a plugin-based scanning mechanism and annotation-driven generation t

go-swagger is a toolkit for working with Swagger/OpenAPI 2.0 specifications in Go. It generates server, client, and CLI code from a specification document, and can also produce a specification by scanning annotated Go source code. The project includes a static validation engine that checks documents against the schema and project-specific rules, and a specification transformation pipeline that resolves, flattens, and merges documents. The toolkit generates both client and server code from the same specification, ensuring consistency in request and response handling. It also produces a command

utoipa is a Rust API documentation tool used to generate machine-readable OpenAPI specifications. It functions as a specification generator and schema mapper that converts Rust structs and enums into compliant OpenAPI schemas. The project distinguishes itself by using procedural macros and traits to automate metadata extraction from code. It supports complex data modeling, including generics, polymorphism, and recursive type resolution, while synchronizing field renaming and tagging from serialization attributes. It also enables the composition of modular specifications, allowing multiple sma

APIJSON is a no-code database API generator and object-relational mapping layer that automatically transforms relational database schemas into functional HTTP endpoints. It provides a system for generating CRUD operations and technical documentation without the need to write manual backend code. The project is distinguished by its ability to allow clients to define custom JSON response structures and field aliases directly within the request. It features dynamic query translation that converts structured JSON parameters into optimized SQL for complex relational joins, subqueries, and data agg

Salvo is a comprehensive Rust web framework for building asynchronous HTTP servers and web applications. It features a hierarchical web router that uses a tree-based structure to map requests to handlers and an asynchronous middleware pipeline based on the onion model for request and response pre- and post-processing. The framework is distinguished by its native support for modern network protocols, including a QUIC-based HTTP/3 implementation alongside HTTP/1 and HTTP/2. It includes an integrated OpenAPI documentation generator that extracts schemas directly from handler signatures to produc

NSwag is a toolchain for the .NET ecosystem designed to automate the generation of API documentation, server controllers, and typed client proxies from OpenAPI contracts. It functions as a contract-first API tool that enables the creation of server-side boilerplate and client libraries based on predefined specifications. The suite distinguishes itself through its ability to extract OpenAPI specifications from existing ASP.NET Core code via reflection and its capacity to generate type-safe TypeScript client proxies. It also provides an interactive documentation server that hosts and renders th

swagger-php is an OpenAPI specification generator and PHP API documentation library. It scans PHP source code attributes and annotations to produce standardized specification files and interactive API references. The tool functions as a schema inference engine that derives data types and schemas from native PHP type hints and generic blocks. It uses reflection-based static analysis to extract metadata without executing application logic and supports recursive schema inheritance to merge definitions from parent classes and interfaces. The project includes a command-line utility for exporting

Sphinx is an extensible documentation framework and multi-format document publisher. It serves as a technical content organizer that converts reStructuredText markup and Python source code comments into structured documentation for technical projects. The system transforms a single set of markup files into multiple output formats, including HTML, LaTeX, EPUB, and Texinfo. It functions as a Python API documentation tool, extracting documentation directly from source code to maintain synchronized technical reference manuals. The framework organizes complex information into hierarchies with aut

Connexion is a spec-first Python web framework designed to derive server behavior and validation logic directly from a predefined API contract. It enables the development of web services by using an OpenAPI specification to automatically handle routing, request validation, and response serialization. The framework distinguishes itself by acting as an OpenAPI request validator and mock server. It can simulate API behavior by serving example responses based on specification schemas, allowing for frontend development and prototyping before a backend implementation is completed. Additionally, it

NSwag is an OpenAPI toolchain for .NET that provides a suite of generators for converting OpenAPI specifications and JSON schemas into clients, server stubs, and structured documentation. It enables the creation of type-safe client libraries and data transfer objects, as well as the generation of OpenAPI specifications by analyzing .NET controllers. The project supports contract-first API development by generating server controller stubs from specifications and offers dedicated TypeScript API integration to ensure type safety in frontend applications. It also provides tools for hosting intera

Knife4j is an enhanced web interface for visualizing and interacting with OpenAPI and Swagger specifications. It serves as a documentation UI and debugging tool that automatically generates technical references from Java source code and web frameworks. The project distinguishes itself through its ability to aggregate API definitions from multiple distributed microservices into a single unified documentation portal. It secures this portal using OAuth2 authentication flows and provides a gateway to restrict access to technical specifications and testing tools. The platform includes capabilitie

gin-swagger is a Swagger UI middleware for the Gin web framework that serves as an OpenAPI 2.0 documentation generator. It provides an interactive REST API sandbox and a browser-based interface for visualizing API contracts and testing endpoints. The project allows for the hosting of multiple API definitions on a single router by assigning each a unique name. It enables the customization of the interface's visual presentation and behavior, including the control of expansion depth and authorization persistence. The middleware intercepts routes to deliver API definitions as JSON payloads and e

Eve is a REST API framework that maps database collections to web resources through declarative configuration files. It functions as a database-to-API mapper, automatically exposing data as RESTful endpoints with built-in support for CRUD operations and schema-based request validation. The project distinguishes itself through a HATEOAS API engine that generates hypermedia links and resource schemas for dynamic client discovery. It also includes an automated Swagger documentation generator that produces interactive specifications for client SDK generation and testing. The framework provides a

ServiceStack is a high-performance .NET web framework designed for building type-safe APIs using strongly-typed request and response objects. It functions as a message-based API engine that decouples business logic from the transport layer, allowing services to be exposed via multiple protocols including HTTP, gRPC, and various message queue providers. The framework is distinguished by its type-safe API generator, which produces native client SDKs and data transfer objects from service metadata across multiple languages. It also includes a distributed service gateway for microservices orchest

yapi is an API management platform designed to coordinate the development of RESTful APIs between frontend, backend, and quality assurance teams. It functions as a centralized system for documenting interface specifications, simulating server responses, and validating requests through a built-in testing client. The platform features an API code generator that transforms interface specifications into typed request functions and data models across multiple programming languages. It also includes a mock server capable of generating synthetic responses using schema-based generators and rule-based

API Platform is a headless content management system engine and framework used to build REST and GraphQL APIs. It utilizes schema-driven generation to automatically produce web endpoints based on predefined data model definitions. The platform focuses on semantic data modeling, using structured classes and ontologies to ensure information is organized for search engines and semantic web tools. It provides an automated OpenAPI specification generator and a declarative system for creating administration dashboards to manage data records without custom frontend code. The system includes capabil

TypeSpec is a language for defining cloud API shapes and generating OpenAPI, JSON Schema, and client/server code from a single source of truth. It functions as a protocol-agnostic API designer that models REST, gRPC, and other API protocols using a unified, extensible syntax, with a decorator-based metadata system for attaching metadata, validation rules, and lifecycle visibility to API models and operations. The compiler produces OpenAPI 3.0 specifications and other artifacts, and the tool supports declaring API versions and tracking changes to models, properties, and operations across releas

This project is a REST-to-gRPC API gateway and JSON reverse proxy that translates RESTful HTTP requests into gRPC service calls. It functions as a protocol buffer proxy generator, providing the tools necessary to bridge JSON-based HTTP traffic with backend gRPC servers. The system distinguishes itself by automating the creation of reverse-proxy servers and stubs through protobuf-driven code generation. It also includes a dedicated OpenAPI specification generator that produces OpenAPI v2 and v3 documents from gRPC service definitions and annotations. The project covers a broad range of integr

Connexion is a specification-driven framework for building APIs that automatically maps OpenAPI specifications to application logic. It uses these specifications to automate routing, request validation, and response serialization, linking API operations to backend handler functions via operation IDs. The project differentiates itself by providing a schema-driven mock server that simulates API behavior using example responses from the specification without requiring backend logic. It also includes a dynamic documentation hosting system that translates the API specification into a live interact

Litestar is a high-performance Python ASGI web framework designed for building asynchronous APIs and web services. It functions as a type-safe toolkit that leverages Python type hints to provide automatic request validation and response serialization, while natively generating interactive API documentation based on the OpenAPI specification. The framework is distinguished by its integrated dependency injection system, which manages shared resources and resolves complex nested service chains directly within request handlers. It further organizes API development through class-based controllers

This project is a comprehensive sample library and implementation guide for ASP.NET Core. It provides a collection of practical examples and projects that demonstrate how to build web applications, RESTful APIs, and high-performance services. The repository focuses on a variety of architectural patterns, including the development of Minimal APIs, contract-first gRPC services, and real-time communication using WebSockets and Server-Sent Events. It includes detailed implementations for user identity and security, such as token-based authentication and CSRF protection. The codebase covers a bro

mcp-context-forge is a Model Context Protocol federation gateway that unifies diverse AI tool servers and APIs into a single consistent interface for discovery and execution. It acts as a centralized proxy that aggregates multiple servers and APIs, allowing AI agents to access and invoke a unified set of tools, prompts, and resources. The project distinguishes itself through a multi-protocol translation bridge that converts communication between standard I/O, SSE, gRPC, and REST to enable interoperability between disparate tool servers. It includes a comprehensive LLM evaluation framework for

openapi-devtools is a browser extension and OpenAPI specification generator that captures network traffic to automatically document the API structures of websites and applications. It functions as an HTTP traffic capturer and browser-based documentation tool, mapping real-time network requests into standardized API specifications. The tool enables API reverse engineering by intercepting outbound HTTP traffic and using heuristic-based merging to combine headers, bodies, and parameters from multiple requests into unified endpoint definitions. These captured definitions can be visualized as huma

mitmproxy2swagger is a tool that transforms captured mitmproxy network traffic into structured OpenAPI schemas for reverse-engineering REST APIs. It functions as an OpenAPI schema converter and network traffic documentation utility, extracting API endpoints and data structures from captured network packets to create formal technical references. The tool enables the reconstruction of undocumented APIs by converting intercepted HTTP request and response patterns into specifications. It supports merging multiple traffic capture files into a single schema to incrementally expand an API map and ut

This project is a centralized API specification registry and governance framework. It serves as a source of truth for structured API schemas, gRPC definitions, and data models used to maintain consistency across a large ecosystem of services. The system functions as a multi-language client generator, transforming standardized interface definitions into executable source code and language-specific libraries. This process ensures that client libraries and technical documentation remain synchronized by deriving them directly from the original interface definitions. The project also covers the m

Doxygen is a source code documentation generator and multi-language API reference tool. It extracts annotated comments from source code to create structured technical manuals and searchable software libraries in formats including HTML, LaTeX, and PDF. The project functions as a static code analysis visualizer, generating call graphs, class diagrams, and inheritance hierarchies to illustrate codebase structure. It also serves as an XML documentation export engine, producing structured metadata that can be transformed via XSLT or third-party tools. Beyond API extraction, the tool provides a Ma

Goa is a design-first Go framework that generates server and client code, documentation, and request validation from a single declarative domain-specific language (DSL). At its core, it provides a Go DSL for defining API endpoints, data types, and error models, which compiles into fully functional HTTP and gRPC server stubs, client packages, and OpenAPI specifications. The framework distinguishes itself through its plugin-extensible code generation pipeline, allowing custom code generation steps, middleware, or transport layers to be added via plugins. It supports multiple transport protocols