API Runner
Free online API testing tool. Send GET, POST, PUT, PATCH, DELETE requests with custom headers, query params, and JSON body. Inspect response headers, status codes, and timing — no signup required.
How to Use API Runner
Open the API Runner tool on toollabs.in — no signup or download required.
Paste or type your input into the editor area. The tool processes everything locally in your browser for maximum privacy.
View the output instantly. Copy the result to your clipboard, download it, or continue working with the formatted data.
All processing happens client-side. Your data never leaves your device, making it safe for sensitive codebases.
Why Use API Runner?
API Runner on toollabs.in is designed to be the fastest, most privacy-respecting option available online. Unlike many alternatives, our tool processes everything directly in your browser — your data never touches our servers.
Whether you're a developer debugging an API, a student learning developer concepts, or a professional working with sensitive data, API Runner provides a reliable, zero-cost solution with no registration required.
Built with modern web standards and optimized for performance, the tool loads instantly and works across all devices — desktop, tablet, and mobile. It even works offline after the initial page load.
100% Free
No subscriptions, no paywalls, no hidden costs
Privacy First
All processing happens in your browser
Lightning Fast
No server latency, instant results
No Signup
Start using immediately, no account needed
Frequently Asked Questions
Is this tool a replacement for Postman?▼
For quick API testing and debugging, yes. It supports all major HTTP methods, custom headers, query parameters, and request bodies. For advanced features like collections and environments, a full desktop client may be more suitable.
Does the API Runner store my requests?▼
Request history is stored locally in your browser's localStorage. No data is ever sent to our servers. You can clear your history at any time.
Why am I getting CORS errors?▼
Browser-based HTTP clients are subject to CORS (Cross-Origin Resource Sharing) policies. If the target API doesn't include 'Access-Control-Allow-Origin' headers, the browser will block the response. This is a browser security feature, not a limitation of this tool.
Can I send authenticated requests?▼
Yes. Add an Authorization header with your Bearer token, API key, or Basic credentials. All header values stay in your browser and are never logged or transmitted to our servers.
Use Cases
API Debugging
Quickly test API endpoints during development without switching to a desktop app
Webhook Testing
Send POST requests to webhook endpoints to verify they're receiving data correctly
Response Inspection
Examine response headers, status codes, timing, and body content in detail
Quick Prototyping
Test third-party APIs before integrating them into your application
Examples
GET Request
Input:
GET https://jsonplaceholder.typicode.com/posts/1
Output:
{ "userId": 1, "id": 1, "title": "...", "body": "..." }POST Request
Input:
POST https://jsonplaceholder.typicode.com/posts
Body: { "title": "foo", "body": "bar" }Output:
{ "id": 101, "title": "foo", "body": "bar" }Related Tools
Explore more free developer tools on toollabs.in