API Contract Tester
Online API contract tester for request execution, response checks, contract assertions, and stress tests in integration and regression workflows.
This tool sends real network requests to the URL you provide. Verify endpoint, headers, and payload before execution.
Request Configuration
Authentication
Request Headers
Response
Response data will appear here after sending request
Response Headers
Response Body
Contract Validation
Stress Test
Request History
Guide
Positioning
API Contract Tester helps teams configure requests, inspect responses, and run rule assertions in browser so integration and regression phases can detect contract drift earlier.
Core Features
- Supports GET, POST, PUT, DELETE, PATCH and multiple content types.
- Supports Bearer, Basic, API Key, OAuth2 setup and custom headers.
- Validates status code, headers, required fields, and response data types.
- Provides concurrent stress testing and request history replay for regression checks.
How To Use
- Choose method and fill URL, auth config, headers, and body values.
- Send request and inspect status, headers, and response payload.
- Enter contract rules and run validation against actual response.
- Run stress test and reuse history records for follow-up checks.
Use Cases
- Quick API contract checks during frontend-backend integration
- Regression validation before release
- Compatibility checks after API changes
- Lightweight stress baseline checks for QA workflow
FAQ
- Will request data be uploaded: no, processing is local in your browser.
- Why can requests fail: common causes are CORS policy or network reachability.
- Must rules be JSON: no, simplified YAML-like text rules are also supported.
- Is stress test equal to professional load tools: no, this is for lightweight checks.
Privacy
This tool does not store or upload your API endpoints, payloads, or response data. Everything runs in the current browser session.