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API Tester & Request Builder Online — Free REST Client Tool

API Request Builder

Build and test HTTP API requests with headers, body, auth, and response visualization.

A lightweight, browser-based HTTP client for building and testing REST API requests. Configure HTTP methods, headers, query parameters, request body, and authentication. View formatted responses with status codes, timing, and headers. Generate code snippets in 14+ languages. Privacy-first with no data stored on servers.

Keywords: api tester, rest client, http request builder, postman alternative, api request tool, http client online, rest api tester, api endpoint tester, free postman, api testing tool, http method tester, request builder online

Tags: api, http, rest, request, postman, client, fetch, endpoint

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How to API Request Builder Online

  1. Enter your API endpoint URL in the URL bar at the top.

  2. Select the HTTP method (GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS) from the dropdown.

  3. Add query parameters, headers, and request body using the tabs below the URL bar.

  4. Configure authentication — Bearer token, Basic auth, or API Key — in the Auth tab.

  5. Click Send or press Cmd+Enter to execute the request and view the formatted response on the right.

API Request Builder Features

  • Support for all HTTP methods: GET, POST, PUT, PATCH, DELETE, HEAD, and OPTIONS.

  • Key-value editors for headers and query parameters with enable/disable toggle per row.

  • Multiple request body types: JSON, Form Data, URL-encoded, and raw text.

  • Built-in authentication support: Bearer token, HTTP Basic auth, and API key (header or query).

  • Response visualization with syntax-highlighted JSON, status code badge, timing, and size.

  • Response headers and cookie viewer with parsed Set-Cookie attributes.

  • Copy response body or copy request as cURL with one click.

  • Import requests from cURL commands pasted from the clipboard.

  • Request history storing your last 20 requests for one-click replay.

  • Server-side proxy for CORS bypass — send requests to any API without browser restrictions.

  • AI-powered response explanations, error analysis, and request improvement suggestions.

  • Keyboard shortcuts for fast workflow: Cmd+Enter to send, Cmd+Shift+C to copy, Cmd+Shift+H for history.

Frequently Asked Questions

Is this a replacement for Postman?
It is a lightweight alternative for quick API testing directly in your browser. For complex workflows, collections, environments, and team collaboration, dedicated API clients like Postman or Insomnia are still recommended. DevFlow API Request Builder is ideal for fast, one-off requests during development.
Are my API requests private?
Requests are proxied through our server to bypass browser CORS restrictions. We do not log or store your request data, URLs, headers, request bodies, or response bodies. The proxy is stateless — your data is never persisted.
Why does it use a server proxy instead of sending requests directly from the browser?
Browsers enforce CORS (Cross-Origin Resource Sharing) security policy which blocks most cross-origin API requests. Without a proxy, most API calls would fail with a CORS error. Our server-side proxy forwards your request to the target URL, returns the response, and never stores any data.
What is the maximum response size?
Responses up to 5 MB are supported. Larger responses will be automatically truncated with a warning. The response body display is also limited to 500 KB for browser performance, but the full size is shown.
Can I import cURL commands?
Yes. Click the 'Import cURL' button to read a cURL command from your clipboard and automatically populate all request fields including URL, method, headers, and request body.
Does it support file uploads?
File uploads via multipart form-data are not supported in the initial version. You can send JSON, URL-encoded, form data (key-value pairs), and raw text bodies.
How does request history work?
The last 20 requests you send are saved to your browser's localStorage. Click the History button to open the history panel and click any entry to reload its full configuration. History is stored locally and never sent to any server.

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