Open Source API Development & Testing Tools
A curated collection of the best open source tools and services for developing Application Programming Interfaces..
See also:API ClientsAPI Infrastructure
Sleek, intuitive API development and testing platform
Stars
80,754Last commit
1 day agoLicense
MIT
Lightweight, fast, and feature-rich API client for developers. Test, debug, and document APIs with ease in a clean, modern interface.
Open Source Alternative to:
Lightweight, fast, and open-source API client for developers
Stars
48,182Last commit
6 hours agoLicense
MIT
A modern, user-friendly API client that simplifies API testing and development with a clean interface and powerful features.
Open Source Alternative to:
Powerful API development and testing made effortless
Stars
40,127Last commit
6 hours agoLicense
Apache-2.0
Intuitive API client for REST, GraphQL, and gRPC. Debug, test, and collaborate on APIs with ease across platforms.
Open Source Alternative to:
Fast, secure, offline API client with Git integration
Stars
19,441Last commit
6 hours agoLicense
MIT
A modern API client offering local-only data storage, Git integration, plugin extensibility, and multi-protocol support for developers.
Open Source Alternative to:
High-performance API gateway with built-in LLM support
Stars
17,293Last commit
7 hours agoLicense
Apache-2.0
Apache APISIX is an open-source API gateway built on NGINX and etcd, offering dynamic routing, 100+ plugins, load balancing, authentication, and traffic management for APIs and LLM workloads.
Open Source Alternative to:
Universal API management for REST, GraphQL, gRPC & async
Stars
10,874Last commit
16 hours agoLicense
Unknown
Fast, scalable API management platform with open source gateway, analytics, dev portal and dashboard. Deploy anywhere with AI-ready governance and security.
Open Source Alternative to:
Effortless API mocking for seamless development
Stars
8,471Last commit
6 hours agoLicense
MIT
Create, run, and share mock REST APIs without coding. Boost productivity with an intuitive interface and powerful features.
Open Source Alternative to:
Intercept, modify, and debug HTTP(S) requests effortlessly
Stars
6,757Last commit
8 hours agoLicense
AGPL-3.0
A powerful browser extension and desktop app for developers to manipulate network requests, debug APIs, and improve web app testing
Open Source Alternative to:
Secure, scalable API key management for developers
Stars
5,483Last commit
6 hours agoLicense
AGPL-3.0
Streamline API authentication with UnKey's powerful, developer-friendly platform for creating, revoking, and monitoring API keys.
Open Source Alternative to:
Modern command-line HTTP client for the API era
Stars
4,056Last commit
2 years agoLicense
BSD-3-Clause
Intuitive, user-friendly CLI tool for making HTTP requests, debugging APIs, and testing web services with ease and efficiency.
Open Source Alternative to:
Blazing-fast API gateway with linear scalability
Stars
2,701Last commit
3 days agoLicense
Apache-2.0
High-performance, stateless API gateway built for microservices. Handle 80K+ requests/second with transparent pricing and enterprise-grade reliability.
Open Source Alternative to:
Unified API development ecosystem for modern teams
Stars
2,620Last commit
8 months agoLicense
AGPL-3.0
All-in-one platform for API testing, documentation, and collaboration, simplifying the entire API development lifecycle.
Open Source Alternative to:
Build APIs like code with Git-native workspace
Stars
Stars declining over the last 30 days1,782Last commit
1 day agoLicense
Apache-2.0
Offline-first API workspace that unifies specs, docs, tests, and mocks in programmable Markdown blocks. Version control everything in plain text files.
Open Source Alternative to:
API management platform for developers and AI agents
Stars
2,128Last commit
10 days agoLicense
Apache-2.0
Open source API management platform that exposes databases as REST, routes microservice traffic, handles billing, and generates SDKs across multiple languages.
Open Source Alternative to:
The modern GraphQL runtime
Stars
1,443Last commit
2 months agoLicense
Apache-2.0
Swiftly design and ship best-practice GraphQL backends atop existing data sources and APIs.
Open Source Alternative to:
Unify APIs, databases, and services effortlessly
Stars
1,285Last commit
7 hours agoLicense
Apache-2.0
A powerful backend framework that simplifies API integration, enhances security, and boosts developer productivity for modern web applications.
Open Source Alternative to:
Fast, secure, offline API client for REST and gRPC
Stars
728Last commit
15 hours agoLicense
BSD-3-Clause
Cross-platform API client offering fast, secure, and offline testing for REST and gRPC services. Available on macOS, Windows, and Linux with intuitive design.
Open Source Alternative to:
Open-source GraphQL federation platform
Stars
482Last commit
16 hours agoLicense
MIT
A fully open-source schema registry, analytics, and gateway for GraphQL federation and APIs
Open Source Alternative to:
Unified API, event, and AI agent management platform
Stars
467Last commit
6 hours agoLicense
Apache-2.0
Full-lifecycle API management platform that unifies synchronous and asynchronous ecosystems. Manage APIs, event streams, and AI agents with enterprise security and 4x faster gateway performance.
Open Source Alternative to:
Capture – Capture screenshots, generate PDFs, scrape content, extract metadata, and automate browsers with one API.
Sent
Capture