API Testing Utilities
Test and debug APIs with our free browser-based tools. Send requests, test WebSockets, build HTTP requests, and generate test tokens.
REST API Client
Send HTTP requests (GET, POST, PUT, DELETE) and inspect responses from your browser.
WebSocket Tester
Connect to WebSocket endpoints, send messages, and inspect frames.
HTTP Status Code Reference
Searchable reference of all HTTP status codes with descriptions and use cases.
Request Builder
Build HTTP requests interactively and generate code snippets in multiple languages.
curl to Fetch Converter
Convert curl commands to JavaScript fetch, Python requests, and more.
OpenAPI Validator
Validate OpenAPI 3.x and Swagger 2.0 specifications for correctness.
Mock API Generator
Generate mock API responses from JSON schemas for rapid development.
Fake Data Generator
Generate realistic fake data including names, emails, phone numbers, addresses, and more.
Featured Guides & Tutorials
Deepen your knowledge with these related guides and tutorials.
Why Use API Testing Tools Online?
Modern web development relies heavily on API integration. Whether you need to test REST APIs online, debug third-party API responses, generate test data, or work with JWT authentication, having the right API development tools streamlines your workflow. Our browser-based utilities let you send HTTP requests, inspect responses, and generate tokens without installing any software or uploading data to external servers.
REST Client & Request Builder
Send HTTP requests to any API endpoint with our REST API tools. Inspect headers and response bodies, and build complex requests with authentication headers.
HTTP Status Code Reference
Quickly look up HTTP status codes by category with our HTTP request tools and reference guide. Understand every response code from 1xx to 5xx.
JWT Generator & Decoder
Generate JWTs for testing authentication flows. Decode and inspect existing tokens to verify claims and expiration times with our API testing tools.
Fake Data Generator
Generate realistic test data including names, emails, addresses, and custom fields for API testing and development using our online utilities.
Best Practices for API Testing
Test REST APIs Online for Error Responses
Do not only test success paths. Verify your application handles 4xx and 5xx responses gracefully when you test REST APIs online.
Use Realistic Test Data
Generate fake data that closely resembles production data structures to catch validation and formatting issues early in development.
Validate JWT Tokens
Always decode and verify JWT tokens during development to ensure correct claims, expiration times, and signature algorithms.
Reference Status Codes
Keep an HTTP status code reference handy during API development. Using the correct status code improves API usability and client compatibility.
Frequently Asked Questions
Are these API testing tools free?
Yes, all API development tools are completely free with no usage limits or sign-up required.
Do you store my API requests?
No. All requests happen locally in your browser. Nothing is stored or transmitted when you use our REST API tools.
Can I test authenticated endpoints?
Yes, our API request builder supports custom headers including Authorization, API keys, and Bearer tokens for authenticated testing.