Postman-style API testing with parallel requests, authentication, payloads, and response diagnostics.
Headers
{
"Accept": "application/json"
}An API client is a tool that lets developers send HTTP requests to any REST API endpoint and inspect the full response, including status codes, headers, and body content. It is essential for building, debugging, and testing backend services without writing throwaway scripts or relying on command-line tools like cURL. Our browser-based API client gives you a Postman-style interface with support for parallel requests, multiple authentication schemes, and real-time response diagnostics — all without installing anything.
Yes, it is completely free with no usage limits. You can send as many requests as you need without creating an account or subscribing to a plan.
All requests are made directly from your browser to the target API. Your credentials, tokens, and request data never pass through our servers. Nothing is stored or logged on our end.
Browser-based API clients are subject to Cross-Origin Resource Sharing (CORS) policies. If the target server does not include the appropriate CORS headers, your browser will block the response. This is a server-side configuration issue, not a limitation of this tool. You can test the same request with a local proxy or ask the API provider to allow your origin.
It sends multiple identical requests to the same endpoint at the same time. This is useful for basic load testing, checking rate limiting behavior, or comparing response consistency across concurrent connections.
Yes. The client supports Bearer token authentication, HTTP Basic Auth, and API key authentication. API keys can be sent as a custom header or as a query parameter depending on what the endpoint expects.
An API client is a tool for crafting and sending HTTP requests to web APIs and inspecting their responses — without writing any code. REST has become the dominant architecture for web APIs, and virtually every modern application — from mobile banking apps to e-commerce platforms — is powered by REST API calls. Understanding how to construct, send, and read API requests is an essential skill for frontend developers, backend engineers, QA teams, and anyone integrating services.
HTTP defines request methods that convey the intended action: GET retrieves data without modifying state; POST creates a new resource; PUT replaces an existing resource; PATCH applies a partial update; DELETE removes a resource. Beyond the method, requests carry headers — metadata like Content-Type, Accept, and Authorization. APIs protect endpoints with Bearer tokens, API keys, and Basic Auth. Every response includes a status code: 200 OK, 201 Created, 400 Bad Request, 401 Unauthorized, 404 Not Found, 500 Internal Server Error.
Reading API responses fluently speeds up development. A good API client formats JSON responses with syntax highlighting and collapsible trees, dramatically reducing debugging time. Browser-based clients require no installation, no account, and work on any device — making them ideal for quick ad-hoc testing, sharing with colleagues, or working from locked-down corporate machines.
An API client is a graphical or browser-based interface for manually constructing HTTP requests — setting the method, URL, headers, and body — and inspecting the full response including status code, headers, and formatted body. It is the interactive complement to curl on the command line, offering a visual layer that makes exploration and debugging faster and more intuitive.
Postman is a full-featured platform with collections, environments, automated test scripts, and team collaboration — powerful, but heavy. A browser-based API client is optimized for speed and accessibility: no installation, no account required, always up to date. For quick requests or sharing with a colleague, browser clients often win on practicality. For large teams managing hundreds of versioned API collections, Postman's ecosystem adds real value.
A Bearer token is an access token included in the HTTP Authorization header to authenticate API requests. The format is: Authorization: Bearer <token>. Whoever holds (bears) the token is granted access — the server does not verify the requester's identity beyond the token. Bearer tokens are commonly JWTs issued by OAuth 2.0 authorization servers, typically with an expiration time, and must be transmitted over HTTPS.
Select POST as the method, enter your endpoint URL, choose "raw JSON" as the body format, and write your JSON payload. Critically, add the header Content-Type: application/json so the server knows how to parse the body. Without this header, many servers will reject or misinterpret the request. This API client handles the Content-Type header automatically when you select JSON mode.
A 401 response means the server requires authentication and either none was provided or what was provided is invalid. Common causes: missing Authorization header, expired Bearer token, incorrect API key, or wrong authentication scheme. A 403 Forbidden response means authentication succeeded but you lack permission. Fixing a 401 always involves examining and correcting your credentials.
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