API Client

Postman-style API testing with parallel requests, authentication, payloads, and response diagnostics.

Authentication

Query Params

Headers

Request Preview

GET https://jsonplaceholder.typicode.com/posts/1

Headers

{
  "Accept": "application/json"
}

Responses

Run a request to see response status, timing, headers, and body.
Overview

Browser-Based API Client — Test Any Endpoint Without Installing Anything

The API Client on sourcecodestack lets you send real HTTP requests directly from your browser to any endpoint you choose. Pick a method, enter a URL, configure headers, query parameters, authentication, and a request body — then fire one request or up to 50 in parallel and inspect every response in full.

Because requests originate from your browser, the data travels to your target API exactly as you configure it — nothing passes through our servers. You can test Bearer tokens, Basic Auth, API key injection (header or query string), set custom Content-Type values, and control per-request timeouts, all without leaving the tab.

100% freeNo sign-upRuns in your browserParallel requests
How to use it
  1. 1Select an HTTP method (GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS) and enter the target URL.
  2. 2Add query parameters and custom headers using the key-value rows, toggling each row on or off as needed.
  3. 3Choose an authentication strategy — Bearer token, Basic Auth, or API Key — and fill in the credentials.
  4. 4For POST/PUT/PATCH requests, paste your request body and confirm the Content-Type.
  5. 5Set the parallel request count and timeout, then click Send to fire all requests simultaneously and review each response.
Key features
  • Seven HTTP methods: GET, POST, PUT, PATCH, DELETE, HEAD, and OPTIONS.
  • Parallel execution up to 50 simultaneous requests with a shared execution summary showing success count, failure count, and average duration.
  • Four authentication modes: None, Bearer Token, Basic Auth (username and password), and API Key (header or query string placement).
  • Per-request and per-header enable/disable toggles so you can try different parameter combinations without deleting rows.
  • Live request preview pane shows the final resolved URL, merged headers, and payload before you send.
  • Configurable per-request timeout in milliseconds to catch slow or unresponsive endpoints.
  • Full response inspection including status code, duration, response size in bytes, headers, and body displayed per request.

Frequently asked questions

Does my data pass through sourcecodestack servers?
No. Requests are sent directly from your browser to the target URL. sourcecodestack servers are not in the request path at any point.
Why do some requests fail with a CORS error?
Browsers enforce the same-origin policy. If the target API does not include the correct Access-Control-Allow-Origin headers, the browser will block the response. This is a browser-level restriction, not a bug in the tool.
Can I test APIs that require authentication?
Yes. The tool supports Bearer Token, HTTP Basic Auth (sent as a Base64-encoded Authorization header), and API Key injection into either a header or a query parameter.
What does parallel request count do?
It sends multiple copies of the same request simultaneously using Promise.all. This is useful for basic load testing or reproducing race conditions, up to a maximum of 50 concurrent requests.
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Full guide

API Client Complete Guide

Explore how to test REST APIs, handle auth, parallel requests, and debug CORS issues.

Test REST & GraphQL APIsHandle auth headers & CORSCommon questions answered

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