What is a REST API? How to Test It and Best Practices
A REST API (Representational State Transfer Application Programming Interface) is a standardised set of rules that allows software applications to communicate over the web using HTTP. REST APIs power nearly every modern digital product — from social media platforms and payment gateways to IoT devices and mobile apps. They expose data and operations via URLs called endpoints, and use standard HTTP verbs: GET to retrieve data, POST to create, PUT to replace, PATCH to partially update, and DELETE to remove resources.
Testing a REST API is an essential step in API development and integration. Effective API testing verifies that endpoints return the correct HTTP status codes, that response payloads conform to the expected schema, and that authentication and authorisation are enforced correctly. Tools like our online REST API tester let you send live HTTP requests directly from your browser without installing anything — making rapid exploration and debugging fast and accessible.
Best practices for REST API testing include: always testing with both valid and invalid input to confirm proper error handling; checking that 401 and 403 responses are returned for unauthenticated and unauthorised requests respectively; verifying Content-Type headers match the response format; and measuring response times to catch performance regressions early. For POST and PUT requests, send a minimal valid body first, then incrementally add fields to confirm validation logic.
When working with REST APIs in production, use HTTPS exclusively, rotate API keys regularly, and always validate response schemas against your expected contract. Our tool supports Bearer token and Basic Auth, SSL verification, and redirect following — giving you a realistic picture of how your API behaves under real conditions. Save frequently-used requests to collections and review your request history to streamline your testing workflow.