API Tester — In-Browser REST Client
Test HTTP API endpoints directly in your browser. Make GET, POST, PUT, PATCH, and DELETE requests with custom headers and request bodies. View status codes, response headers, and pretty-printed JSON responses — all client-side, no server proxy.
How to Use API Tester — In-Browser REST Client
How to Use the API Tester:
Select HTTP Method: Choose GET, POST, PUT, PATCH, DELETE, or HEAD from the method dropdown.
Enter the URL: Type or paste the full endpoint URL including https://. Press Enter or click Send to dispatch the request.
Configure Headers: Open the Headers tab to add, edit, or disable request headers. Two defaults (Content-Type and Accept) are pre-filled — uncheck or remove them as needed.
Add a Request Body (POST/PUT/PATCH): Open the Body tab and enter your payload. Typically JSON:
{
"name": "Alice",
"email": "alice@example.com"
}
- Read the Response: The response panel shows the HTTP status code, duration in milliseconds, all response headers, and the body — automatically pretty-printed if it is valid JSON.
HTTP Methods:
- GET — Retrieve data. No body. Safe and idempotent.
- POST — Create a resource. Body required.
- PUT — Replace a resource. Full body required.
- PATCH — Partial update. Send only the fields to change.
- DELETE — Remove a resource. Usually no body.
- HEAD — Like GET but returns headers only. Useful for checking if a resource exists.
Common Request Headers:
- Content-Type: application/json — body is JSON
- Authorization: Bearer <token> — JWT or OAuth token
- X-API-Key: <key> — custom API key header
- Accept: application/json — request JSON response
CORS Limitations: Browsers enforce CORS policies. If the target API does not send appropriate CORS headers, your browser blocks the request. This is a browser security feature. For APIs that block browsers, use curl or Postman from your terminal instead.
Privacy: All requests are sent directly from your browser to the target server. Nothing passes through 100Plus Tools servers. URLs, headers, and bodies are not stored or logged.
Common Status Codes:
- 200 OK — request succeeded
- 201 Created — resource created
- 204 No Content — success, no body
- 400 Bad Request — invalid input
- 401 Unauthorized — authentication required
- 403 Forbidden — not allowed
- 404 Not Found — resource does not exist
- 422 Unprocessable Entity — validation failed
- 429 Too Many Requests — rate limited
- 500 Internal Server Error — server-side error
Frequently Asked Questions
Most Viewed Tools
TOTP Code Generator — 2FA Testing Tool
Generate time-based one-time passwords from a TOTP secret key. Enter your base32 secret, choose a period and digit length, and get the current and next codes with a live countdown timer. Useful for testing and debugging 2FA integrations.
Use Tool →JSON to Zod — Schema Generator
Generate Zod validation schema code from a JSON sample object. Infers z.string(), z.number(), z.boolean(), z.array(), z.object(), and z.null() types automatically. Handles nested objects, arrays of objects with optional field detection, and outputs copy-ready TypeScript with import and z.infer type alias.
Use Tool →JSONL Formatter — Line-by-Line Validator
Format, validate, and inspect JSON Lines (JSONL) and NDJSON files. Validates each line individually, reports parse errors by line number, outputs compact JSONL or a pretty-print preview, and lets you download the cleaned file.
Use Tool →Screen Size Converter — Diagonal Dimension Tool
Calculate screen width and height from diagonal size and aspect ratio. Convert between inches and centimeters for displays, TVs, and monitors with instant dimension calculations.
Use Tool →Password Entropy Calculator — Crack Time Estimator
Calculate the information-theoretic bit entropy of any password or API key. Detects character set pools automatically, shows the total number of possible combinations, and estimates crack time across five attack scenarios from rate-limited web logins to GPU cracking clusters.
Use Tool →TLS Cipher Suite Checker — Strength Analyzer
Check TLS protocol version compatibility and cipher suite strength ratings against current best practices. Supports IANA and OpenSSL cipher names — rates each suite as Strong, Weak, or Deprecated and explains why.
Use Tool →Secret Scanner — API Key & Credential Detector
Scan pasted text, code, or config files for accidentally exposed API keys, tokens, passwords, and private keys. Detects 50+ secret types across AWS, GitHub, Stripe, OpenAI, and more — all client-side, nothing leaves your browser.
Use Tool →TOML Config Validator — Syntax Error Finder
Validate TOML configuration file syntax and report errors with line numbers. Paste any TOML content — Cargo.toml, pyproject.toml, config.toml — and instantly see a green checkmark with key counts and structure stats, or a precise error message pointing to the exact line. Includes a collapsible JSON structure preview to confirm what was parsed.
Use Tool →Related API & Backend Tools
API Diff Checker — Response Comparison Tool
Compare two API response payloads and highlight added, removed, and changed fields. Paste any two JSON responses to get an instant field-level diff with color-coded changes and a summary count.
Use Tool →REST Endpoint Documenter — Markdown Doc Generator
Document a REST endpoint quickly by entering the URL, method, headers, and sample request/response. Generates formatted Markdown documentation and an example cURL command instantly.
Use Tool →OAuth Token Validator — JWT & OIDC Decoder
Validate and inspect OAuth tokens in your browser. Decode JWT access tokens and ID tokens to view claims, scopes, and expiry. Analyse opaque tokens for entropy and format. Free and private.
Use Tool →API Mock Data Generator — Realistic JSON Builder
Generate structured, realistic mock data for API endpoint testing. Define fields with names and types — UUID, name, email, integer, enum, date, and more — set how many rows you need, and export as a JSON array, NDJSON, or CSV. All generation runs entirely in your browser with no data sent to any server.
Use Tool →OpenAPI Mock Generator — Turn API Specs into Live Mock Servers
Paste an OpenAPI 3.x or Swagger 2.0 spec, select any endpoint, and instantly get a realistic mock request body and response matching the defined schemas. Also generates a ready-to-run cURL command.
Use Tool →Webhook Retry Config Calculator — Simulate Exponential Backoff & Jitter
Configure exponential backoff parameters and preview the full retry schedule for webhook delivery. Enter max attempts, initial delay, multiplier, jitter, and a max delay cap to instantly see each retry timestamp, cumulative elapsed time, jitter range, and which delays hit the cap. Supports presets for standard, aggressive, conservative, Stripe-style, and fixed-interval retry policies. Free and runs entirely in your browser.
Use Tool →Webhook Validator — Payload & Signature Checker
Validate and inspect webhook payloads in your browser. Auto-detects GitHub, Stripe, Slack, and Shopify webhooks, extracts event details, and optionally verifies HMAC signatures. Free and private.
Use Tool →CORS Header Generator — Cross-Origin Config Tool
Build CORS configuration headers interactively for web servers and APIs. Set allowed origins, methods, request headers, credentials, and preflight cache duration — then copy the generated Access-Control headers or ready-to-paste code snippets for nginx, Express.js, Flask, and .NET.
Use Tool →Share Your Feedback
Help us improve this tool by sharing your experience