API Tester — Online REST Client

What is an API tester?

An API tester (or REST client) lets you send HTTP requests to a web service and inspect exactly what comes back — without writing code. Developers use it to explore third-party APIs, debug webhooks, check authentication, reproduce bug reports and verify an endpoint before wiring it into a frontend. This tool covers the everyday core of desktop apps like Postman or Insomnia, with nothing to install and no account.

Anatomy of an HTTP request

• Method — what you want to do: GET reads, POST creates, PUT replaces, PATCH partially updates, DELETE removes. HEAD returns headers only, OPTIONS asks which methods are allowed.
• URL & query parameters — e.g. /v1/users?page=2&limit=50. Values are URL-encoded automatically when you edit them in the Params table.
• Headers — metadata such as Accept: application/json, Content-Type or an API key header.
• Body — the payload for POST/PUT/PATCH. JSON bodies are sent with Content-Type: application/json; form bodies with application/x-www-form-urlencoded.
• Auth — Bearer sends Authorization: Bearer <token> (OAuth 2.0, JWT). Basic sends Authorization: Basic base64(user:password).

Reading the response

The status code tells you what happened — 2xx success, 3xx redirect, 4xx a problem with your request (401 missing auth, 404 wrong path, 422 validation error), 5xx a server failure. Look each one up in our HTTP Status Codes reference. Response time is measured from our server to the API, and size is the body size in bytes. Inspect content-type, rate-limit headers (x-ratelimit-remaining, retry-after) and caching headers in the Headers tab.

Why requests go through our server

Browsers block cross-origin requests unless the API sends CORS headers, which most server-to-server APIs don’t. Sending the request from our server avoids CORS entirely, so you see the API’s real response. For safety, requests to localhost, private IP ranges and cloud metadata addresses are blocked; to test a local API, use curl — the Copy as cURL button generates the command for you, and our cURL to Code converter turns it into JavaScript, Python or PHP.

Is it safe to use with real credentials?

Your request passes through our server only to be forwarded; it isn’t logged or stored. History is kept in your own browser and excludes Authorization, Cookie and API-key headers. Still, prefer test keys or short-lived tokens for any online tool, and decode JWTs locally with the JWT Decoder.

Tools that pair well with the API Tester

• Base64 Encode / Decode — Convert text to Base64 and back with full UTF-8 support (accents, emoji), switch to URL-safe Base64, or drop a file to get its Base64 string or data URI.
• What Is My IP — Your public IP address and everything your browser reveals to the websites you visit — user agent, screen, language, timezone and request headers.
• User Agent Parser — Decode any User-Agent string into browser, engine, operating system and device — and find out whether it belongs to a search engine, AI crawler or script.
• DNS Lookup — Query all common DNS record types for a domain in one go, with TTLs, sorted MX records and an SPF/DMARC email-authentication summary.