How to Test a REST API with Postman

2026-09-12
By Đội Ngũ Toidayhoc
4 Min Read

Understand the REST API Request

A laptop beside connected request and response panels on a clean desk

Before opening Postman, identify what the API expects and what it should return. A request usually contains an HTTP method, a URL, headers, query parameters, and sometimes a request body. For example, a product API might use GET https://api.example.com/products/42 to retrieve product 42, while POST https://api.example.com/products creates a new product.

Start with the API documentation and write down the required method, endpoint, authentication method, and data format. Check whether the service expects JSON, form data, or query parameters such as category=books. This preparation prevents a common beginner mistake: changing several settings at once without knowing which part caused the failure.

Create a Postman Workspace and Environment

A single computer screen showing organized API request folders and environment controls

Create a Postman workspace for the project and group requests into folders such as Users, Products, and Orders. Keeping related requests together makes it easier to repeat a workflow and compare results. A small project may need only ten requests, but clear organization becomes valuable when the collection grows to dozens of endpoints.

Use environment variables for values that change between development, staging, and production. Instead of typing the full server address into every request, store it as a base URL variable and reference it consistently. The same approach works for an access token, user ID, or API version, while reducing accidental requests to the wrong server and avoiding repeated edits.

Send a GET Request First

A developer reviewing a successful data response beside a web service diagram

A GET request is a useful first check because it normally reads data without changing the server. Enter the endpoint, select GET, add any required authorization, and send the request. If the endpoint is https://api.example.com/users/15, verify that the response represents user 15 rather than simply confirming that the server returned something.