API Request Builder
Developer UtilitiesBuild and test HTTP API requests with method, headers, body, authentication, and query parameters — inspect full response in your browser.. Free, private — all processing in your browser.
The API Request Builder lets you construct and send HTTP requests directly from your browser with full control over method, URL, headers, query parameters, request body, and authentication. Test REST APIs, GraphQL endpoints, webhooks, and any HTTP service without installing a separate REST client. See the full response — status code, headers, body (formatted as JSON if applicable), response time, and size — in a clean interface built for debugging.
Configure requests through dedicated tabs: URL with query string builder, headers form, body editor with content-type switching (JSON, form-urlencoded, multipart, raw text, XML), authentication (Bearer, Basic, custom), and cookies. Save request configurations for later. Generate cURL commands or code snippets (Python, JavaScript, Go, etc.) from any built request for use in your applications. All requests run from your browser — we never see your API keys or endpoints.
API Request Builder — key features
Full HTTP method support
GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS — all standard methods.
Body editor with types
JSON (formatted), form-urlencoded, multipart (file upload), XML, raw text — each with appropriate input.
Authentication presets
None, Basic Auth, Bearer Token, API Key, with credentials stored locally.
Response inspector
Status, headers, body (formatted), time, size all displayed clearly.
Query parameter builder
Structured key-value inputs for query params with automatic URL encoding.
History and saved requests
Recent requests saved locally for quick recall.
Code generation
Export any request as cURL, Python requests, JavaScript fetch, or other language.
Client-side only
API keys and request data stay in your browser; we don’t proxy or log.
How to use the API Request Builder
- 1
Enter URL
Type the API endpoint URL.
- 2
Pick method
GET, POST, PUT, DELETE, etc. depending on what you’re testing.
- 3
Configure headers
Add Content-Type, Authorization, and any custom headers.
- 4
Add body if needed
For POST/PUT/PATCH, use the body editor with appropriate format.
- 5
Send and inspect
Click send; review status, headers, body, and timing of the response.
Common use cases for the API Request Builder
API development
- →Endpoint testing: Verify your API endpoints return expected responses during development.
- →Error reproduction: Reproduce user-reported errors by crafting the exact request they made.
- →Auth flow testing: Test authentication schemes — OAuth token exchange, JWT issuance, API key validation.
Integration testing
- →Third-party API exploration: Learn how a new API works by sending test requests and reviewing responses.
- →Webhook testing: Trigger webhooks manually and inspect the payloads your server receives.
- →SDK verification: Compare requests from an SDK against direct API calls to debug SDK issues.
Documentation
- →Code sample generation: Build a working request, then export as code samples for API documentation.
- →Client library debugging: Compare what your client library actually sends vs. what’s documented.
- →Training: Teach junior developers how HTTP APIs work by walking through request construction.
API Request Builder — examples
Simple GET
Fetch a resource.
GET https://api.example.com/users/42
200 OK
48ms
{
\"id\": 42,
\"name\": \"Ana Kowalski\",
\"email\": \"ana@example.com\"
}POST JSON
Create a resource.
POST https://api.example.com/users with JSON body
201 Created headers include Location: /users/43 response body shows created resource
With Bearer token
Authenticated request.
GET https://api.example.com/private, Authorization: Bearer xxx
200 OK if token valid 401 if token missing or invalid 403 if authenticated but not authorized
Form upload
Multipart with file.
POST https://api.example.com/upload with multipart/form-data
uploads file, API returns 200 with file metadata
CORS error
Browser blocks cross-origin request.
GET https://some-api.com from devtools-hub
error: CORS blocked by browser fix: API must return Access-Control-Allow-Origin header, or use server-side proxy
Technical details
The API Request Builder handles all common HTTP request patterns:
Methods: GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS. PATCH is common for partial updates; PUT for full replacements.
URL construction:
- Base URL + path
- Query parameters via structured key-value inputs
- URL encoding handled automatically
- Supports path parameters via template syntax (/users/{id})
Headers: key-value form. Common headers (Content-Type, Authorization, Accept, User-Agent) available as quick-add. Custom headers supported.
Body types:
- application/json: JSON editor with formatting
- application/x-www-form-urlencoded: key-value form
- multipart/form-data: file upload support
- application/xml: raw XML editor
- text/plain: raw text
- binary: file upload
Content-Type is set automatically based on body type but can be overridden.
Authentication:
- None
- Basic Auth: username/password base64-encoded to Authorization: Basic ...
- Bearer Token: Authorization: Bearer {token}
- API Key: custom header or query param with key name
- OAuth 2.0: abbreviated flow support via redirect
Response display:
- Status code with color-coded indicator (green 2xx, yellow 3xx, red 4xx/5xx)
- Response time in ms
- Size in bytes or KB
- Headers table
- Body: JSON formatted (with syntax highlighting), raw, pretty, preview, or hex for binary
- Error messages for network failures, CORS blocks, timeouts
CORS considerations: the browser enforces CORS for cross-origin requests. Some APIs require their clients to be whitelisted or provide CORS headers. If a request fails due to CORS, it\u2019s a browser limitation — the server is not at fault. Workarounds: use a CORS proxy, run requests server-side, or ask the API to add proper CORS headers.
Saved requests: store configuration locally (localStorage) for quick recall. Request history tracks recent requests for reference.
Code generation: export any built request as cURL, Python requests, JavaScript fetch, or other language snippet for use in your applications.
Common problems and solutions
⚠CORS blocks request
Browsers enforce CORS for cross-origin requests. If API doesn’t return Access-Control-Allow-Origin, requests fail. Workaround: use a CORS proxy, run server-side, or convince the API owner to add CORS headers.
⚠Content-Type mismatch
Setting the wrong Content-Type breaks body parsing on the server. JSON body needs application/json; form data needs application/x-www-form-urlencoded. The tool sets correct type based on body editor mode.
⚠URL encoding in query params
Query parameters with special characters need URL encoding. The tool encodes automatically; verify the encoded URL matches what you expect in the request preview.
⚠Authorization header format
Bearer tokens need \"Bearer \" prefix (with space). Basic auth is base64(user:pass) with \"Basic \" prefix. Wrong format returns 401.
⚠Cookies not sent
By default, cross-origin requests don’t include cookies. Enable credentials option if the API requires cookies.
⚠Timeout on slow APIs
Default timeout may be too short for slow APIs. Increase timeout setting for requests that take long.
⚠API rate limits
Many APIs limit requests per minute. Hitting the limit returns 429. Check API documentation for rate limits and add delays between requests if necessary.
API Request Builder — comparisons and alternatives
Compared to Postman or Insomnia, this tool is instant — no install, no account, no sync. For occasional use or quick testing, this tool is faster. For heavy API work (teams, environments, test scripts), Postman\u2019s features win.
Compared to curl in a terminal, this tool has a GUI with formatted response display. CLI is better for scripting; this tool is better for interactive exploration.
Compared to Python requests or JavaScript fetch in code, this tool doesn\u2019t require writing code to test. Code is better for repeatable tests; this tool is better for one-off debugging.
Frequently asked questions about the API Request Builder
▶How do I test an API endpoint?
Enter the URL, pick the method (GET, POST, etc.), add any required headers (auth, Content-Type), provide the body for POST/PUT, and click send. The tool shows the full response including status, headers, and formatted body.
▶Can I use this for authenticated APIs?
Yes. Configure authentication in the Auth tab: Basic, Bearer Token, API Key, or custom headers. The tool sends credentials with each request; they’re stored only in your browser’s local storage.
▶What about CORS?
Browsers enforce CORS. Cross-origin requests may fail if the target API doesn’t return Access-Control-Allow-Origin headers. You’ll see a clear error message. Workarounds: ask the API owner to enable CORS, use a CORS proxy, or test from a server-side environment.
▶Can I save requests?
Yes. Save any configured request with a name for later recall. Stored in browser localStorage — no account needed, data stays local.
▶How does this compare to Postman?
Similar core functionality. Postman has more features (team workspaces, environments, mock servers, test scripts). This tool is faster to use for quick ad-hoc requests without installing anything. For heavy API development, Postman or Insomnia is more powerful.
▶Can I test GraphQL?
Yes. Use POST with Content-Type: application/json and body: {\"query\": \"your graphql query\"}. The tool handles the JSON format correctly. For GraphQL-specific tooling, GraphiQL or Apollo Studio offer better query editors.
▶How do I upload files?
Switch body mode to multipart/form-data. Add a file field by clicking the file icon next to the value input. Browser file picker opens; select the file to upload.
▶Is my request data private?
All request configuration and sending runs in your browser. We don’t proxy requests, don’t see your API keys, and don’t log anything. Saved requests are stored locally in your browser.
Additional resources
- MDN Fetch API — Browser fetch API used internally by this tool.
- RFC 9110 HTTP Semantics — Authoritative HTTP specification for understanding request semantics.
- Postman — Industry-standard API development platform for deeper testing needs.
- CORS explained — Background on cross-origin resource sharing, critical for understanding browser-based API tools.
- httpstatuses.com — Quick reference for HTTP status codes you’ll encounter while testing APIs.
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