100% Local · Light Postman Client · Fast HTTP requests

    API Tester

    Lightweight, in-browser REST client. Test HTTP endpoints with custom parameters, headers, bodies, and auth configurations securely.

    Encrypted browser sandbox Zero data logging
    ParameterValue

    Enter a URL and click Send to make a request

    Browser Sandbox (CORS Enforced)CORS Active

    Browser blocks cross-origin requests without CORS headers. Run the Desktop Agent to bypass.

    Desktop Companion Agent
    Offline

    How It Works

    Bypass browser CORS, mixed-content blocks, and localhost restrictions. The agent runs locally on your machine with 100% privacy — no cloud proxies.

    Step 1
    Download
    • Click the download button above
    • Windows .exe · macOS .command · Linux .deb/.rpm
    • Or use the raw Python script (zero pip deps)
    Step 2
    Run
    • Double-click the downloaded file
    • A console opens on 127.0.0.1:45456
    • Keep it open while testing
    Step 3
    Allow Loopback
    • Click the tune (sliders) or 🔒 lock icon left of URL
    • Toggle "Apps on device" → Allow
    • Refresh the page (one-time Chrome permission)
    Step 4
    Test
    • Agent auto-connects instantly
    • Green "Agent Active" badge appears
    • All requests bypass CORS natively
    Zero CORS · Full localhost access
    Loopback Only
    127.0.0.1 — no external access
    Zero Cloud Relay
    Direct machine-to-server
    Zero Dependencies
    Python std library only
    1-Click Shutdown
    Stop anytime from web UI
    Verify agent is running: Run in any terminal
    curl http://127.0.0.1:45456/health
    Developer Reference

    Free Online REST API Client with Multi-Tab Sessions

    A lightweight, free, and secure browser-based Postman alternative. Test GET, POST, PUT, and DELETE requests across up to 6 independent tab sessions — complete with auth, parameters, body editors, and instant response inspection. No install. No login.

    Multi-Tab Sessions

    Up to 6 isolated request tabs — each with its own URL, auth, body, and response.

    100% Local

    All HTTP calls execute in your browser. Zero server relay. Credentials stay private.

    Full Auth Support

    Basic Auth (with password reveal), Bearer, JWT, and API Key in header or query.

    Rich Response View

    Status badges, response time, body size, raw headers, and formatted JSON output.

    Multi-Tab API Session Manager
    New

    The tab bar at the top of the tool works exactly like browser tabs — each pill is an entirely separate request context. Open a GET in one tab, a POST in another, and a Bearer-authenticated DELETE in a third, all visible side-by-side without any state bleeding between them.

    Add Tab ( + )

    Click the + button on the right of the tab bar to open a fresh, blank request context. Up to 6 tabs allowed.

    Switch Tabs

    Click any tab pill to instantly switch. Your previous URL, method, body, auth, and response are all preserved.

    Method Badge

    Each tab pill shows a colour-coded method badge (GET green, POST indigo, PUT amber, DELETE red) for at-a-glance identification.

    Live Spinner

    A spinning indicator appears on the tab pill while its request is in-flight, so you always know which tab is loading.

    Reset Current Tab

    The ↺ reset button clears only the active tab's state — URL, params, body, auth, and response — leaving all other tabs untouched.

    6-Tab Hard Cap

    To maintain performance, the + button is disabled once you reach 6 tabs. Close an existing tab to open a new one.

    Why Use an Online HTTP / API Client?

    API Clients are foundational utilities during backend and frontend integrations. Instead of writing curl commands or installing desktop software, this visual tool lets you structure endpoints, configure auth, and inspect responses inside a clean browser interface — instantly accessible from any device.

    Our tool is a lightweight Postman alternative that loads in seconds with no registration, no installation, and no cloud sync. It is ideal for verifying public APIs, validating webhook destinations, checking JSON schema outputs, and running multiple endpoint tests in parallel using the multi-tab session feature.

    HTTP Request Anatomy

    Every API request contains key building blocks that dictate how servers process payloads:

    Core Request Architecture
    METHOD   →  GET, POST, PUT, DELETE
    URL      →  https://api.domain.com/v1/users
    PARAMS   →  ?page=1&limit=20  (auto-appended)
    HEADERS  →  Authorization: Bearer <token>
                Content-Type: application/json
    BODY     →  { "username": "dev_coder" }
    
    RESPONSE →  STATUS (200 OK, 404 Not Found…)
                HEADERS (Cache-Control, ETag…)
                BODY (JSON, HTML, plain text)

    Supported Authentication Methods

    Configure per-tab authentication without affecting other open sessions. Each auth type is isolated to the tab it was set in.

    Auth TypeHow It WorksSent AsExtra Feature
    Basic AuthBase64-encodes username:password automaticallyAuthorization: Basic …👁 Password visibility toggle
    Bearer TokenPrefixes your raw token stringAuthorization: Bearer …—
    JWTSends JSON Web Token as a BearerAuthorization: Bearer …—
    API KeyCustom key name + valueHeader or Query paramConfigurable location
    NoneNo auth header added——

    Basic Auth — Password Visibility Toggle

    The password field in the Basic Auth panel includes an eye (👁) icon button. Clicking it reveals the password in plain text so you can verify the exact credentials before sending. The toggle is per-tab — different tabs can independently show or hide their passwords. Credentials are encoded only in your browser and never stored externally.

    Method Examples

    HTTP request templates — inspect & copy

    Select any method below to view standard configurations. Open each in a different tab to test them in parallel.

    Request URL
    GET https://jsonplaceholder.typicode.com/todos/1
    Headers: Accept: application/json
    Body Payload
    None

    💡 Retrieves a representation of a resource. Ideal for fetching user data, configuration, or item lists. Open a new tab and paste this URL to test simultaneously.

    CLI & Browser Synergy

    Bidirectional cURL Integration: Import & Export in 1-Click

    Seamlessly bridge terminal commands with visual debugging. Convert raw terminal cURL snippets into rich, editable UI tabs, and export active sessions back to standardized cURL scripts in seconds.

    RFC 7230 Compliant
    Zero Dependencies

    Smart cURL ImportCLI → UI

    Paste from DevTools, Postman, Swagger, or terminal docs

    Click Import cURL in the top header. Our client-side parser parses complex command strings into their constituent parts:

    HTTP Method: Auto-detects -X POST, -X PUT, -X DELETE, -X PATCH (defaults to GET)
    URL & Parameters: Splits query strings directly into the interactive key-value Params table
    Headers & Auth: Maps -H headers, -u Basic credentials, and Bearer / JWT tokens cleanly
    Request Payloads: Parses --data, -d, and --data-raw into formatted JSON or raw text
    Example: DevTools & Terminal SyntaxSupported
    curl -X POST "https://api.example.com/v1/auth/login" \
      -H "Content-Type: application/json" \
      -H "Accept: application/json" \
      --data '{"email":"developer@company.com"}'

    One-Click cURL ExportUI → CLI

    Export your configured request to standardized terminal commands

    Click Export cURL in the bottom bar or header to generate formatted, production-ready bash commands:

    Smart State Detection: Disabled automatically when a request tab is fresh or has no endpoint URL
    Multi-Line Escaping: Formatted with backslashes (\) for seamless pasting into bash, zsh, or PowerShell
    Full Auth Preserved: Includes Basic Auth (-u), Bearer tokens, custom headers, and query parameters
    Instant Clipboard: One-click copy with immediate visual feedback toast and clean modal preview
    Generated Export OutputReady to execute
    curl -X POST "https://api.example.com/v1/orders" \
      -H "Authorization: Bearer eyJhbGciOi..." \
      -H "Content-Type: application/json" \
      -d '{"itemId": 42, "quantity": 1}'
    Browser DevTools to UI

    Right-click any failed network call in Chrome, Firefox, or Safari DevTools, click Copy as cURL, and paste it straight into JsonifyTools to inspect and replay.

    Team Reproductions & Jira

    Export exact request reproductions into Slack, Jira tickets, or pull requests so backend teammates can instantly test and verify the same bug report.

    CI/CD & Automation

    Prototype requests visually with parameter auto-completion, then export the verified cURL command directly into GitHub Actions or deployment scripts.

    Common HTTP Methods Comparison

    Understanding standard HTTP semantics is essential when designing REST integrations. Use a separate tab for each method to test your full CRUD API surface in one view.

    MethodIdempotentHas Request BodyPurpose
    GETYesNoFetch details of a resource without side effects.
    POSTNoYesCreate a new resource on the server.
    PUTYesYesReplace or update a complete resource model.
    DELETEYesNoPermanently remove a resource by ID.
    HTTP Status Guide

    HTTP Status Codes Quick Reference

    When you dispatch requests using our online API tester, the response panel displays the exact status code returned by your server:

    200 OK

    Standard response for successful GET, PUT, or POST requests.

    201 Created

    The request succeeded and a new resource was created (common for POST).

    204 No Content

    Request processed successfully, but no content body is returned (common for DELETE).

    400 Bad Request

    Server cannot process request due to malformed JSON body or invalid syntax.

    401 Unauthorized

    Authentication failed or missing Authorization header (Basic Auth / Bearer / JWT).

    403 Forbidden

    Authenticated user does not have permission to access the specified endpoint resource.

    404 Not Found

    Target URL endpoint path or resource ID does not exist on the server.

    422 Unprocessable Entity

    Request payload is well-formed JSON but fails backend validation rules.

    500 Internal Error

    Unhandled exception or error occurred on the target API server.

    Programmatic REST Request Snippets

    Easily translate your test requests into production code across popular programming languages:

    cURL Command
    curl -X POST "https://api.example.com/v1/users" \
      -H "Authorization: Bearer <your_jwt_token>" \
      -H "Content-Type: application/json" \
      -d '{"name": "Jane Doe", "role": "Developer"}'
    JavaScript Fetch (Browser / Node)
    const response = await fetch('https://api.example.com/v1/users', {
      method: 'POST',
      headers: {
        'Authorization': 'Bearer ' + token,
        'Content-Type': 'application/json'
      },
      body: JSON.stringify({ name: 'Jane Doe', role: 'Developer' })
    });
    const data = await response.json();
    Python Requests
    import requests
    
    url = "https://api.example.com/v1/users"
    headers = {
        "Authorization": "Bearer " + token,
        "Content-Type": "application/json"
    }
    payload = {"name": "Jane Doe", "role": "Developer"}
    
    response = requests.post(url, json=payload, headers=headers)
    print(response.json())
    Go (Golang http.Client)
    req, _ := http.NewRequest("POST", "https://api.example.com/v1/users", body)
    req.Header.Set("Authorization", "Bearer "+token)
    req.Header.Set("Content-Type", "application/json")
    
    client := &http.Client{}
    resp, err := client.Do(req)

    How to Test an API — Step-by-Step

    1

    Open a Request Tab

    A fresh tab opens automatically. Click '+' to add up to 5 more tabs for parallel endpoint testing across GET, POST, PUT, and DELETE.

    2

    Enter URL & Method

    Type your endpoint URL and choose the HTTP method. Paste a URL with a query string and the tool will auto-extract parameters into the Params tab.

    3

    Configure Auth

    Go to the Auth tab. Choose Basic Auth (use the eye icon to verify your password), Bearer Token, JWT, or API Key with header/query placement.

    4

    Set Headers & Body

    Add custom request headers in the Headers tab. Switch to Body to set a JSON or plain-text payload for POST and PUT requests.

    5

    Send & Inspect

    Hit 'Send'. The response panel shows status code, time in ms, body size, formatted JSON or raw text output, and all response headers.

    6

    Reset or Switch Tab

    Hit ↺ Reset to clear the current tab for a fresh call. Switch to another tab to compare responses without losing your work.

    API Testing Scenarios
    • JSON Response Validation — verify schemas match expected shapes
    • Auth Token Verification — test header authentication across different tab configs
    • Speed Benchmarking — compare roundtrip latency across multiple endpoints in parallel
    • CORS Checking — detect cross-origin policy issues in browser sandboxes
    • Parameter Debugging — test complex query strings and body parsers side by side
    • Credential Auditing — use the Basic Auth password toggle to verify credentials before sending
    Key Tool Features
    • Multi-tab sessions — up to 6 fully isolated request contexts
    • Per-tab reset button — clears only the active tab, other tabs untouched
    • Chrome-style tab bar with method badges, live spinner, and close buttons
    • GET, POST, PUT, and DELETE HTTP methods
    • URL parameter auto-extraction into editable key-value rows
    • Basic Auth with password visibility toggle (👁 icon)
    • Bearer token, JWT, and API Key (header or query) authentication
    • JSON and plain-text request body editors
    • Timing metrics — response time in milliseconds, body size in bytes
    • Full response parser — status code, formatted body, and all headers
    • 100% client-side sandbox — credentials never leave your browser
    • No install, no registration, no cloud sync required
    Zero-CORS Companion Service · Localhost & Intranet

    Desktop Companion Agent: Bypass Browser CORS & Test Any API Natively

    Web browsers enforce strict sandbox rules that block cross-origin calls, localhost endpoints, and private networks. The JsonifyTools Companion Agent is a lightweight, local helper service that dispatches requests natively on your operating system with zero restrictions.

    Port 45456 Active Bridge
    The Problem: Browser Sandboxing & CORS
    • ✕Strict CORS Block: Modern browsers refuse cross-origin HTTP calls unless target servers send exact Access-Control-Allow-Origin headers.
    • ✕Blocked Localhost & Docker: HTTPS web apps cannot call http://localhost:3000 or local microservices due to browser Mixed Content & Private Network Access blocks.
    • ✕Stripped Request Headers: Browsers silently drop or forbid critical headers like User-Agent, Cookie, Host, and Origin.
    • ✕Self-Signed SSL Failures: Local staging microservices running self-signed development certificates trigger fatal SSL exceptions in browser engines.
    The Solution: Desktop Companion Agent
    • ✓Zero CORS Restrictions: Requests are executed natively outside the browser runtime, returning complete responses with zero cross-origin errors.
    • ✓Full Localhost & LAN Access: Effortlessly test APIs running on 127.0.0.1, localhost:8080, Docker containers, and corporate intranet subnets.
    • ✓100% Header Fidelity: Transmits custom User-Agent, session cookies, and authentication headers exactly as you defined them with zero stripping.
    • ✓Permissive SSL Testing: Includes built-in support for dev certificates, self-signed microservices, and internal staging environments.
    Why It's 100% Secure, Easy & Transparent
    Local Loopback Only

    The agent listens exclusively on 127.0.0.1:45456. It is completely inaccessible from the outside internet or local Wi-Fi.

    Zero Cloud Relaying

    Your API requests travel directly from your computer to your target server. No payload, auth header, or response body ever touches an external third-party proxy.

    Pure Standard Library

    Built with Python's standard library with zero external pip packages. The complete source code is open and inspectable in under 300 lines of clean code.

    Instant One-Click Control

    Start the agent whenever you need native testing, and cleanly terminate it at any time by clicking the Stop Agent button in the UI or pressing Ctrl+C.

    Available Native Packages for All Platforms

    Free download · No telemetry · No sign-up
    Windows (.exe)
    8.5 MB

    Single standalone executable. Double-click to run. Requires zero installation and no Python setup. Runs a clean local console on port 45456.

    Standalone Executable
    macOS (.command)
    1.0 KB

    Double-click command script that leverages macOS's built-in python3, or run via our 1-liner curl install command.

    Native Python3 Script
    Linux (.deb / .rpm)
    ~3.5 KB

    Official packages for Ubuntu/Debian (.deb · 3.9 KB) and Fedora/RHEL (.rpm · 3.5 KB) for native system package managers.

    Debian & Red Hat Packages
    Universal Python
    10 KB

    Run anywhere with python jsonifytools_agent.py. Compatible with Python 3.8+ on Windows, macOS, Linux, FreeBSD, and WSL.

    Cross-Platform Script
    How The Agent Architecture Connects
    Zero-CORS Request Lifecycle
    Step 1 · Client
    JsonifyTools Web UI

    You configure tabs, auth, headers, and body payloads in the browser.

    ↓127.0.0.1:45456
    Local Loopback
    Step 2 · Bridge
    Desktop Companion Agent

    Dispatches HTTP calls natively via OS sockets outside browser CORS sandboxes.

    ↓Native Socket
    Zero CORS Block
    Step 3 · Target
    Target API Endpoint

    localhost:3000, Docker containers, private LANs, or external cloud APIs.

    Security and Privacy Guarantee

    Unlike desktop tools that aggregate histories and sync credentials to centralized cloud services, this web client is completely local and private. Every fetch runs sandboxed in your browser's native Fetch API. No request data, headers, tokens, or body payloads ever touch our servers.

    Multi-tab session data lives entirely in React component state for the lifetime of the page. Refreshing or closing the tab clears everything instantly. API keys set in one tab are isolated from all other tabs by design — no accidental credential bleed between sessions.

    💡 Tip: Ensure your target API is served over HTTPS to protect transmission across local networks. Basic Auth credentials are Base64-encoded in-browser — always use HTTPS in production.

    Frequently Asked Questions

    Everything about multi-tab sessions, authentication, CORS, reset, and privacy.

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