Open Source API Development & Testing Software
API Development & Testing tools provide environments for designing, debugging, and documenting application interfaces. These tools handle requests across protocols like REST, GraphQL, and WebSockets to verify that endpoints return the correct data. This type of software is for developers who need to manage traffic routing and test microservices. Self-hosting these apps ensures that sensitive request headers, authentication tokens, and internal endpoint schemas remain on private infrastructure. This approach allows teams to version control their API collections using local files instead of relying on external cloud storage.
This page lists 42 open source tools in the API Development & Testing category. The most popular are Hoppscotch, Caddy and Traefik. Most use the Apache-2.0 or MIT license, and 34 offer an official Docker image.
Hoppscotch
Test, debug, and document APIs using a lightweight client that supports multiple protocols and team collaboration.
Caddy
An extensible web server platform that provides automatic HTTPS by default for all hosted sites.
Traefik
An HTTP reverse proxy and load balancer that automatically configures routes for microservices in cloud environments.
Bruno
An offline API client that stores collections on the local filesystem for version control via Git.
Kong
A cloud native API and AI gateway for managing traffic, routing, and LLM orchestration.
Insomnia
A cross platform API client for debugging, designing, and testing REST, GraphQL, gRPC, and WebSocket protocols.
Hasura
Generate a composable and secure API endpoint to access data from multiple database sources.
NGINX
A web server and reverse proxy that provides load balancing, content caching, and API gateway capabilities.
Yaak
A privacy-first desktop API client supporting REST, GraphQL, gRPC, and WebSockets with local-only data storage and Git integration.
Windmill
A developer platform for building internal APIs, background jobs, workflows, and UIs using a code first approach.
Scalar
Generates interactive API documentation and provides an offline first client for testing OpenAPI and Swagger specifications.
imgproxy
A standalone server for resizing, processing, and converting images on the fly via HTTP requests.
Mockoon
Design and run mock REST APIs locally to reduce dependency on external services during software development.
massCode
A local first developer workspace combining code snippets, markdown notes, and an integrated HTTP client.
Bifrost
Unify access to multiple AI providers through a single OpenAI compatible API with built in governance.
Requestly
Build and test REST and GraphQL APIs with local storage and Git synchronization for developer collaboration.
Reqable
Capture and analyze network traffic while testing REST APIs across desktop and mobile platforms.
RWKV Runner
A management tool for RWKV models that provides an OpenAI compatible API for local LLM execution.
Open-Meteo
An open-source weather API providing global forecasts and historical data for non-commercial software projects.
Altair
A GraphQL client IDE for debugging queries and implementations across multiple desktop and browser platforms.
Zoraxy
A general purpose HTTP reverse proxy and forwarding tool written in Go for managing web services.
MQTTX
Connect to and test MQTT brokers using a cross-platform client with a chat-like graphical interface.
Kinto
A minimalist JSON document store providing synchronization and sharing capabilities for web and mobile applications.
Judge0
A sandboxed online code execution system for running untrusted code across multiple programming languages.
HTTPie
A command line and desktop client for making HTTP requests and testing REST APIs via terminal.
Bknd
A lightweight backend as a service providing database management, authentication, media storage, and automated workflows.
Svix
A webhook service that manages deliverability, retries, and security for developers via a single API call.
Stoat
Self-hostable group chat with servers, channels, voice, and moderation tools built under EU privacy law.
TileServer GL
Host and serve vector and raster map tiles with GL styles for various web and mobile clients.
Fusio
Self-hosted API management platform to transform internal infrastructure into scalable API products for humans and AI agents.
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