What is SchemaClient?

SchemaClient is a free API testing tool and REST API client for desktop. It lets developers send API requests, test REST APIs, debug HTTP responses, tunnel localhost to a public URL, monitor API traffic in real-time, and validate API schemas — all in one native app for Windows, macOS, and Linux.

Is SchemaClient a free Postman alternative?

Yes, SchemaClient is the best free Postman alternative and Insomnia alternative. Unlike Postman, it includes built-in localhost tunneling, real-time API monitoring, and schema validation at no cost. No subscription, no usage limits, no credit card required.

How do I test REST APIs with SchemaClient?

Open SchemaClient, enter your API endpoint URL, select the HTTP method (GET, POST, PUT, DELETE, PATCH), add headers and request body, then click Send. You can inspect the API response including status code, response headers, response body, and response time. Save requests in collections for reuse.

How does the localhost tunneling tool work?

SchemaClient's tunneling tool exposes your localhost to the internet with a public HTTPS URL. Start your local server, click Start Tunnel, and get a URL like https://your-id.schemaclient.com. Perfect for webhook testing, API demos, and mobile app development. It's a free ngrok alternative built into the API client.

What is the API traffic monitor?

The API monitor is a real-time HTTP traffic inspector that shows every API request and response flowing through your tunnel. Filter by HTTP method, status code, or path. Inspect request headers, response bodies, timing, and size. Essential for API debugging and testing webhooks.

Does SchemaClient support API schema validation?

Yes, SchemaClient includes a built-in API schema validator. Define expected response structures, validate JSON responses against schemas, and catch API contract violations early. Supports OpenAPI and Swagger import to auto-generate API collections.

What platforms does SchemaClient support?

SchemaClient is a cross-platform API testing tool available for Windows 10/11, macOS 12+, and Linux. It also has a mobile companion app for Android and iOS for testing APIs on the go.

Secure Tunnels

Real-Time Monitor

Schema Validation

Cloud Sync

FREE Native Desktop App — Built with Tauri + React

YOUR API COMMAND
CENTER.

Send API requests. Tunnel your localhost to the web. Monitor every HTTP packet in real-time. Validate payloads against strict schemas. All from one lightweight desktop app.

Download for Desktop Explore Features

SchemaClient — API Workspace

v2.0

Request

GET https://myapp.schemaclienttunnel.schemaclient.com/api/users SEND

Headers Body Auth Params

200 OK 12ms 2.1 KB Schema valid

// Response body

{

"users": [

{ "id": 1, "name": "Alice", "role": "admin" },

{ "id": 2, "name": "Bob", "role": "editor" }

]

}

API Client

Send & test requests

Localhost Tunnels

Expose local APIs publicly

Schema Validation

Enforce API contracts

HTTP Methods Supported

Auth Types Built-In

500+

Logs Per Session

Desktop Platforms

CORE CAPABILITIES

/sys/modules — Everything you need to build, test, and debug APIs

REST API Client

Build and send HTTP requests with a full-featured editor. Supports GET, POST, PUT, PATCH, DELETE, HEAD, and OPTIONS with multi-tab workspaces for parallel API testing.

Localhost Tunnels

Expose your local server to the internet with a secure public URL. Each tunnel gets a unique subdomain — share it with your team or use it for webhook testing.

Real-Time Monitor

Watch every HTTP request and response flowing through your tunnel in real-time. Inspect method, path, status, duration, headers, and full body content as it happens.

Schema Validation

Define request and response schemas with field-level constraints — types, min/max length, patterns, enums, and more. Validate live API traffic against your contracts automatically.

OpenAPI Import

Import your existing OpenAPI 3.0 or Swagger specs in JSON and YAML. SchemaClient automatically converts them into validation schemas — no manual configuration needed.

Collections & Cloud Sync

Organize API requests into named collections with base URLs, variables, and auth configs. Sign in to sync your collections and schemas across all your devices via the cloud.

Multi-Tab Workspace

Work on multiple API requests simultaneously with independent tabs.

4 Auth Types

Basic, Bearer Token, API Key, and OAuth2 authentication built-in.

JSON / Form / Raw

Send JSON, form-data, URL-encoded, raw text, or binary file bodies.

Dark & Light Themes

Switch between dark and light mode to match your workflow preference.

HOW IT WORKS

/proc/pipeline — From download to production-ready testing

01.

Download & Launch

Install SchemaClient on Windows, macOS, or Linux. It launches as a lightweight native desktop app powered by Tauri.
02.

Build & Send Requests

Use the built-in API client to craft requests with custom headers, auth, query params, and body payloads. View responses instantly.
03.

Create a Tunnel

Point a tunnel at your local server (e.g. localhost:8000). You'll get a public URL like myapp.schemaclienttunnel.schemaclient.com — shareable instantly.
04.

Monitor Traffic

Every request flowing through your tunnel is captured in the monitor — method, path, status, headers, body, and timing.
05.

Validate with Schemas

Define or import schemas for your endpoints. Every API payload is validated in real-time — catch type mismatches and missing fields instantly.
06.

Save & Sync

Organize requests into collections. Sign in to sync your collections and schemas across devices via the cloud.

Tunnel Architecture

Client

Browser / App

→

Gateway

Public URL

→

WebSocket

Secure Tunnel

→

Localhost

Your Server

API Request Builder

GET /users POST /orders PUT /settings +

GET https://api.example.com/v1/users?page=1 SEND

Auth: Bearer Token Collection: My API

200 OK 14ms 3.2 KB Schema valid

{ "data": [...], "total": 42 }

TRAFFIC MONITOR

/dev/proxy — Intercept, inspect, and validate every request in real-time

● Monitor — Tunnel: myapp

Public: myapp.schemaclienttunnel.schemaclient.com CONNECTED

Method	Path	Status	Time	Size	Schema
GET	/api/v1/users	200	12ms	2.1K	✓
POST	/api/v1/orders	201	45ms	890B	✓
POST	/api/v1/payments	400	8ms	340B	✗
PUT	/api/v1/users/42	200	23ms	1.4K	✓
DELETE	/api/v1/sessions/abc	204	6ms	0B	—
GET	/api/v1/products?page=2	200	34ms	8.7K	✓

6 requests captured Schema violations: 1 | Passed: 5

Full Request Inspection

Click any row to inspect the complete request and response — headers, body, cookies, status, and timing breakdown.

Live Schema Validation

Attach schemas to your monitor. Every request and response payload is validated against your contracts as traffic flows through.

Search & Filter Logs

Filter traffic by method, status, or path. Search through up to 500 request logs per session to find exactly what you need.

USE CASES

/usr/scenarios — Built for developers who need more than just a request sender

Webhook Development

Expose your local server with a tunnel and use the public URL as a webhook callback. Monitor incoming webhook payloads in real-time and validate them against your expected schema.

Team API Demos

Share your local API with teammates via a tunnel URL. They can test against your development server without deploying, while you monitor all their requests live in the traffic monitor.

API Contract Testing

Import your OpenAPI spec, then validate every API response against the defined schema. Catch missing fields, wrong types, and contract violations before they reach production.

Frontend-Backend Integration

Debug API calls between your frontend and backend by routing traffic through SchemaClient's monitor. See exactly what your frontend sends and what your backend returns.

CROSS-PLATFORM

/bin/targets — Built with Tauri for native performance on every desktop

Windows

x64 / ARM64

macOS

Universal Binary

Linux

AppImage / .deb

Powered by Tauri — the Rust-based framework for building tiny, fast desktop apps. SchemaClient uses native webviews instead of bundling a full browser, keeping the install size under 15 MB.

[ FREE & OPEN SOURCE ]

TAKE CONTROL OF
YOUR API WORKFLOW

Stop switching between tunneling tools, API clients, and browser dev tools. SchemaClient gives you request building, tunneling, traffic monitoring, schema validation, and cloud sync — all in one native desktop app.

Download for Desktop View on GitHub

Windows x64 / ARM64 macOS Universal Linux AppImage / .deb

No account required for local usage. Sign in to enable cloud sync for collections and schemas.

YOUR API COMMAND CENTER.

CORE CAPABILITIES

REST API Client

Localhost Tunnels

Real-Time Monitor

Schema Validation

OpenAPI Import

Collections & Cloud Sync

HOW IT WORKS

TRAFFIC MONITOR

USE CASES

Webhook Development

Team API Demos

API Contract Testing

Frontend-Backend Integration

CROSS-PLATFORM

TAKE CONTROL OFYOUR API WORKFLOW

YOUR API COMMAND
CENTER.

TAKE CONTROL OF
YOUR API WORKFLOW