API Testing Tool Features
All-in-One API Testing & Development Tool
SchemaClient combines a REST API client, localhost tunneling tool, real-time API traffic monitor, webhook tester, and schema validator into one free native desktop app. The best free Postman and ngrok alternative.
REST API Client & API Tester
Test REST APIs with full control over HTTP methods, headers, query parameters, and request body. Send API requests, inspect responses, debug HTTP errors, and check API endpoints. Supports JSON, form data, multipart uploads, and raw payloads.
- ✓ GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS
- ✓ Basic, bearer, and API-key authentication
- ✓ Syntax-highlighted JSON response viewer
- ✓ Response timing, headers, and status codes
GraphQL Client
Query GraphQL APIs with a dedicated GQL mode: write queries in a purpose-built editor, pass variables as JSON, and read data and errors in the same response viewer as REST. Same collections, same auth, same workflow.
- ✓ Query editor with variables as JSON
- ✓ Data and errors surfaced side by side
- ✓ Saves into collections like any request
- ✓ Works with bearer, basic, and API-key auth
Localhost Tunnel — Free ngrok Alternative
Expose localhost to the internet with a public HTTPS URL. The best free ngrok alternative for webhook testing, API demos, mobile app development, and sharing local servers with teammates.
- ✓ Instant public HTTPS URLs
- ✓ WebSocket-based for low latency
- ✓ Stable subdomain per user
- ✓ Request/response forwarding with full headers
API Traffic Monitor & HTTP Debugger
Real-time API monitoring tool to watch every HTTP request and response flowing through your tunnel. Debug API calls, inspect headers, request/response bodies, timing, and status codes. Essential for webhook testing and API debugging.
- ✓ Live request/response streaming
- ✓ Filter by method, status, path
- ✓ Response time tracking
- ✓ Promote any capture into a collection
API Schema Validation & JSON Checker
Validate API responses against schemas written in a purpose-built language. Define expected response structures, catch API contract violations early, and ensure your REST APIs return exactly what your frontend expects.
- ✓ Custom schema definitions with format presets
- ✓ Auto-validate live responses
- ✓ Type checking and field validation
- ✓ Cloud-synced schemas
OpenAPI Import Tool
Import OpenAPI 3.x specifications to auto-generate API request collections. Convert your API documentation into testable requests instantly, or draft schemas straight from observed traffic.
- ✓ OpenAPI 3.x specs
- ✓ Auto-generate requests from spec
- ✓ Organized folder structure
API Collections & Cloud Sync
Organize API requests into collections with folders and tags. Save API endpoints, sync API collections across devices, manage authentication, and set base URLs. Like Postman collections but free.
- ✓ Organize with folders and tags
- ✓ Cloud sync across devices
- ✓ Auth inheritance (Bearer, Basic, API Key)
- ✓ Conflict-safe revisions — no lost edits
Team Workspaces & Collaboration
Share collections and schemas with your team in role-based workspaces. Invite by link — no email server, no seat forms — and let everyone test against the same canonical setup.
- ✓ Owner, Admin, Editor, and Viewer roles
- ✓ Share-link invites that work in Slack or a ticket
- ✓ Workspace-scoped collections and schemas
- ✓ Conflict-checked sync protects concurrent edits