Freemium
Insomnia
Open SourceAPI Clients · API Tools
Open-source API client for REST, GraphQL and gRPC by Kong.
apirestgraphqlgrpc
Discover the 23 best open-source tools for api tools. Community-driven, transparent source code with permissive licenses. Curated, compared, and updated for developers.
| Tool | Pricing | Platforms | Top Strength | Link |
|---|---|---|---|---|
| Insomnia | freemium | desktop | Open-source API client for REST, GraphQL and gRPC by Kong. | Details → |
| Hoppscotch | freemium | web | Lightweight, open-source API development ecosystem in the browser. | Details → |
| Bruno | freemium | desktop | Requests are plain files in your repo — versioned with the code | Details → |
| Swagger | freemium | web | OpenAPI tooling suite by SmartBear: UI, editor, codegen and more. | Details → |
| HTTPie | freemium | cli | User-friendly HTTP client for the CLI with JSON-first syntax. | Details → |
| Mockoon | free | desktop, cli | Easy, open-source tool to run mock REST API servers locally. | Details → |
| WireMock | free | cli, web | Flexible API mocking and service virtualization for HTTP. | Details → |
| Requestly | freemium | web, extension | Open-source HTTP interception: modify requests, mock, and debug in browser. | Details → |
| SoapUI | freemium | desktop | API testing tool specialized in SOAP and REST services. | Details → |
| httpbin | free | web | HTTP request and response service for testing clients. | Details → |
Showing top 10 of 23. Browse the full grid below.
API Clients · API Tools
Open-source API client for REST, GraphQL and gRPC by Kong.
API Clients · API Tools
Lightweight, open-source API development ecosystem in the browser.
API Clients · API Tools
Fast, Git-friendly open-source API client that stores collections locally.
API Documentation · API Tools
OpenAPI tooling suite by SmartBear: UI, editor, codegen and more.
API Clients · API Tools
User-friendly HTTP client for the CLI with JSON-first syntax.
API Mocking · API Tools
Easy, open-source tool to run mock REST API servers locally.
API Mocking · API Tools
Flexible API mocking and service virtualization for HTTP.
Tunneling & Debugging · API Tools
Open-source HTTP interception: modify requests, mock, and debug in browser.
API Testing · API Tools
API testing tool specialized in SOAP and REST services.
API Mocking · API Tools
HTTP request and response service for testing clients.
API Mocking · API Tools
Instantly inspect and test incoming webhooks with a temporary URL.
Authentication · API Tools
Open-source authentication for Next.js and other JS frameworks.
Authentication · API Tools
Open-source identity and access management with SSO and SAML.
API Documentation · API Tools
Beautiful OpenAPI docs and modern API client, open source.
API Documentation · API Tools
OpenAPI linting, bundling and three-panel reference docs.
Tunneling & Debugging · API Tools
One-click HTTP interception, inspection and mocking for any stack.
API Clients · API Tools
Offline-first, open-source API client for REST, GraphQL and gRPC.
Authentication · API Tools
TypeScript-first schema validation with static type inference.
Authentication · API Tools
Framework-agnostic TypeScript authentication library (trending).
Email · API Tools
Self-hosted email testing tool with a web UI, catches local mail.
Payments · API Tools
Open-source payments and monetization for developers — checkouts, subscriptions and license keys, MoR model.
Authentication · API Tools
Open-source auth infrastructure with a beautiful admin console — OIDC/OAuth, SSO and user management, self-hostable.
Scheduling & Booking · API Tools
Open-source scheduling infrastructure — Calendly alternative with booking links, teams and an API you can self-host.