API Tester

static · no server Black & White Studio
Params 0
Auth
Headers 0
Body
Query Parameters
Synced with the URL above — edit either side.
Response will appear here.
Body
Headers
Raw
Send a request to see the response.

Free Online API Tester — a lightweight Postman alternative

API Tester is a free, browser-based REST API client. Build and send HTTP requests, manage headers, authentication and request bodies, and inspect formatted JSON responses — all without installing software, creating an account, or running a server. Everything happens locally in your browser, so your tokens and data never leave your device.

All HTTP methods

Send GET, POST, PUT, PATCH, DELETE, HEAD and OPTIONS requests to any REST endpoint.

Headers & query params

Add custom request headers and edit query parameters that stay in sync with the URL.

Auth tokens

Set a Bearer, Basic or API-key token once and have it applied automatically to every request.

JSON & form bodies

Send JSON, x-www-form-urlencoded, multipart form-data or raw text bodies.

cURL import

Paste a cURL command into the URL field to instantly recreate the whole request.

Validate & format JSON

View responses with syntax highlighting, and validate, format or minify JSON instantly.

How to test an API

  1. Pick an HTTP method and enter your endpoint URL — or paste a curl command to auto-fill everything.
  2. Add any request headers and set an authentication token in the Auth tab.
  3. Choose a body type (JSON, form-urlencoded, multipart, or raw) and enter the payload.
  4. Click Send and review the status code, response time, headers and formatted JSON body.

Frequently asked questions

Is this API tester free?

Yes — it is completely free with no sign-up, no account, and no usage limits.

Do I need to run a server?

No. It is a single static page that runs entirely in your browser. You can open the file directly or host it on any static host.

Can I convert a cURL command into a request?

Yes. Paste any curl command into the URL field and the method, URL, headers, auth and body are filled in for you.

Is my data private?

Yes. Requests go straight from your browser to the API. Auth tokens and request history are stored only in your browser's local storage.

Why do some requests fail with a network or CORS error?

Browsers enforce CORS: if an API does not return permissive CORS headers, the browser blocks the response. This is a browser security rule, not a bug in the tool. Tick Bypass CORS (or click Retry with CORS bypass on the error) to relay the request through our server, which is not subject to CORS — your request is forwarded as-is and never stored.