API & Webhook Playground

Instantly test APIs, fire webhooks, and debug requests right from your browser. Zero setup. No account required. 100% Free & Private.

Key
Value

Response

Awaiting Execution

Enter an endpoint URL on the left, define your payloads, and hit SEND to invoke the proxy.

Try a Sample Payload

Master Your Integrations with the Ultimate API Playground

Welcome to the definitive browser-based API Tester. Say goodbye to downloading massive desktop applications, dealing with mandatory account creations, or navigating paywalled limits. The CosmoxHub API Playground runs 100% inside your chromium engine.

Postman Alternative

Why wait 45 seconds for a heavy Electron app to load just to ping an endpoint? We built this tool for pure, frictionless velocity. Insert your URL, execute the payload, review the JSON. No telemetry tracking, zero bloatware.

Bypassing CORS Securely

Browser CORS policies traditionally block native client-side fetch requests. We engineered a proprietary Edge Proxy router that processes your payload statelessly and bounces it instantly without logging records or exposing your keys.

How to Test Webhooks Instantly

Building a Zapier integration or a Make.com scenario? Use the POST method selector, construct your JSON payload matching the platform documentation, and fire directly into their Webhook Catchers to simulate live environments.

Supported Architectures:

  • RESTful Architecture: Full CRUD operations (GET, POST, PUT, DELETE, PATCH).
  • GraphQL: Pass your operations mapping inside the Body tab using explicit JSON structure.
  • OAuth & Bearer Schemes: Seamless mapping through the Auth execution panel.

Latest Post

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Top lightweight Postman alternatives for API Testing

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Security

Understanding CORS & How API Proxies Work

A deep dive into why browsers block cross-origin requests, what CORS actually means, and how edge proxies can solve this securely.

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Guides

How to Test Webhook Catchers (Zapier, Make)

Learn how to instantly fire mocked JSON payloads into webhooks to build and troubleshoot your automation scenarios quickly.

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