API Tester lets you send HTTP requests to any API and inspect the response — no installation needed.
Select a method (GET, POST, PUT…) from the dropdown on the left.
Type or paste a URL in the address bar.
Click Send (or press Enter) to fire the request.
The response body, status code, time, and size appear in the panel below.
Try clicking any example in the sidebar to pre-fill a working request instantly.
Request Tabs
Params
Add URL query parameters as key-value pairs. They are appended to the URL automatically (e.g. ?key=value).
Headers
Add custom HTTP headers. Type a header name — common names are suggested in the dropdown. Values are also suggested for known headers.
Body
Send a request body with POST/PUT/PATCH. Choose JSON, Text, or Form format. JSON is validated before sending.
Auth
Attach authentication automatically. Supports Bearer Token, Basic Auth (username + password), and API Key header.
CORS Proxy
Browsers block requests to APIs that don't allow cross-origin access. If you see a CORS error:
Click the Proxy button next to Send — it turns highlighted when active.
Your request is routed through corsproxy.io which adds the required CORS headers.
Disable the proxy for APIs that already support CORS (e.g. GitHub, JSONPlaceholder).
The error message will remind you to enable the proxy if a CORS block is detected.
Response Panel
Body tab — shows the response with JSON syntax highlighting.
Headers tab — lists all response headers returned by the server.
The status badge (e.g. 200 OK), response time in ms, and size in bytes/KB are shown at the top.
Click Copy to copy the raw response body to your clipboard.
Drag the divider bar between the request and response panels to resize them.
History & Examples
History (top of sidebar) — the last 50 requests are saved automatically. Click any entry to reload it.
Click ✕ Clear to wipe the history.
Examples (bottom of sidebar) — 15 pre-built requests to public APIs. Click one to load it, then hit Send.
Themes
Click any coloured dot in the top-right to switch themes. Your choice is remembered across sessions. Available themes: White, Gradient, Dark, Ocean, Forest, Orange, Rose.
Tips & Shortcuts
Press Enter in the URL bar to send the request.
Header name fields have a built-in dropdown of common HTTP headers.
Header value fields suggest common values (e.g. Content-Type options).
The API Key header name field also has common key header suggestions.
JSON bodies are validated before sending — invalid JSON shows an error.
The tool works fully offline once loaded (no external dependencies).