API Tester

Test any REST API directly from your browser. No install required.

Note: Some APIs may not work due to CORS restrictions. This tool works best with public APIs.
⚡ Try an Example— click any to load instantly
Ctrl+Enter to send

JSON Formatter

Paste any JSON to format or minify
Output will appear here…

This tool runs entirely in your browser. No data is stored or transmitted to our servers.

Free Online API Tester – Test REST APIs Instantly

APISmash is a completely free, browser-based API testing platform designed for developers who want to test REST endpoints quickly and effortlessly. Whether you're debugging a backend API, exploring a public third-party service, or validating your new endpoint before deployment — APISmash has everything you need, all running directly in your browser with zero installation.

Unlike traditional API clients that require software installation or account creation, APISmash operates entirely on the client side. Your API keys, request bodies, headers, and responses never leave your machine. There is no server in the middle processing your data — just your browser and the API you're targeting.

APISmash supports all major HTTP methods — GET, POST, PUT, DELETE, and PATCH. You can add custom request headers, query parameters, and JSON body payloads with a clean, tab-based interface. The response viewer provides syntax-highlighted JSON output, raw text view, and response header inspection — making it easy to understand exactly what the server returned.

Advanced features include: save requests to LocalStorage for future use, request history tracking, code generation (fetch / axios / curl), built-in JSON formatter, environment variable substitution with{{variable}} syntax, response size indicators, one-click JSON download, and color-coded HTTP status codes. Power users can trigger a send action with Ctrl+Enter directly from the keyboard.

APISmash is built and maintained by Rohit Siva Shankar, a 2nd Year Mathematics and Computing student at IIT Guwahati, as part of the CodeSmash suite of developer productivity tools. The platform is designed to be fast, minimal, and developer-friendly — because great tools should get out of the way and let you focus on what matters: building amazing software.