Open Source API Development & Testing Tools

A curated collection of the best free and open source tools for building and exercising APIs, covering clients, gateways, mocking, documentation and contract testing.

Hoppscotch

Browser-based API development platform for building, sending and testing requests across REST, GraphQL, WebSocket and MQTT, solo or with a team.

Alternative to:

Postman

Sleek, intuitive API development and testing platform

Stars
80,701
Forks
6,189
Last commit
2 days ago

Bruno

An offline API client that stores collections as plain text files in your repository, so Git handles versioning and team sharing.

Alternative to:

Postman

Lightweight, fast, and open-source API client for developers

Stars
47,883

HTTPie

A command-line HTTP client with natural syntax and colorized output, made for testing, debugging and poking at APIs by hand.

Alternative to:

Postman

Modern command-line HTTP client for the API era

Stars
38,676

Yaak

Offline-first desktop API client for REST, GraphQL, gRPC, WebSocket and SSE, for developers who want no telemetry or cloud lock-in.

Alternative to:

Postman

Fast, secure, offline API client with Git integration

Stars
19,376

Apache APISIX

Dynamic API gateway built on NGINX and etcd, handling traffic routing, security and LLM proxying for microservice platforms.

Alternative to:

Amazon API Gateway

High-performance API gateway with built-in LLM support

Stars
17,258

Scalar

Toolkit that renders OpenAPI documents as an interactive API reference and pairs it with an offline-first API client.

Alternative to:

Postman

Open-source API documentation and testing platform

Stars
16,330

Tyk

Open source API gateway supporting REST, GraphQL, gRPC and TCP, with authentication, rate limiting and analytics included.

Alternative to:

Amazon API Gateway

Universal API management for REST, GraphQL, gRPC & async

Stars
10,870

Mockoon

A desktop app and CLI for designing and running mock APIs locally, for developers who need fake endpoints without deploying anything.

Alternative to:

Beeceptor

Effortless API mocking for seamless development

Stars
8,462

UnKey

A source-available developer platform for API infrastructure, covering key issuance, rate limiting, gateways, permissions and usage analytics.

Alternative to:

Amazon API Gateway

Secure, scalable API key management for developers

Stars
5,480

Requestly

A Git-native desktop API client for designing, testing and sharing HTTP requests, with local, team-synced or self-hosted storage.

Alternative to:

Postman

Intercept, modify, and debug HTTP(S) requests effortlessly

Stars
6,755

Krakend

A stateless API gateway that aggregates, transforms and secures backend endpoints for teams moving to microservices or backend for frontend layers.

Alternative to:

Amazon API Gateway

Blazing-fast API gateway with linear scalability

Stars
2,697

Firecamp

A multi-protocol API client for Rest, GraphQL, WebSocket and Socket.IO, built for teams that design, test and share collections.

Alternative to:

Postman

Unified API development ecosystem for modern teams

Stars
2,617

Voiden

An offline, Git-native API workspace where requests, tests, and documentation live together in plain-text files you version like code.

Alternative to:

Postman

Build APIs like code with Git-native workspace

Stars
1,919

WunderGraph

Lifecycle API management platform for federated GraphQL, covering schema registry, composition checks, routing, analytics, metrics and tracing.

Alternative to:

Apollo GraphOS

Unify APIs, databases, and services effortlessly

Stars
1,283

Hive

Schema registry and analytics platform for GraphQL federation, available as a managed cloud service or self-hosted on your own infrastructure.

Alternative to:

Apollo GraphOS

Open-source GraphQL federation platform

Stars
483

Gravitee

An API management platform that controls who reaches your APIs and when, for organizations exposing services to internal and external consumers.

Alternative to:

Amazon API Gateway

Unified API, event, and AI agent management platform

Stars
462

Stars
Forks
Last commit

Stars
Forks
Last commit

Stars
Forks
Last commit

Stars
Forks
Last commit

Stars
Forks
Last commit

Stars
Forks
Last commit

Open Source API Development & Testing Tools

A curated collection of the best free and open source tools for building and exercising APIs, covering clients, gateways, mocking, documentation and contract testing.

Hoppscotch

Bruno

HTTPie

Yaak

Apache APISIX

Scalar

Tyk

Mockoon

UnKey

Requestly

Krakend

Firecamp

Voiden

WunderGraph

Hive

Gravitee

Hoppscotch

Bruno

HTTPie

Yaak

Apache APISIX

Scalar

Tyk

Mockoon

UnKey

Requestly

Krakend

Firecamp

Voiden

WunderGraph

Hive

Gravitee

Insomnia