Skip to content
Postman API Testing Tips

How To Use Collection Variables In Postman

API Testing Blog

How to Use Collection Variables in Postman for Effective API Testing

Collection variables are a powerful feature in Postman that allows you to store and reuse data across multiple requests within a collection. This makes your tests more efficient, flexible, and maintainable. Here’s a comprehensive guide on how to use collection variables in Postman for your API testing needs.

1. Defining Collection Variables

Step 1: Open your Postman collection and navigate to the Variables tab.

Step 2: Click on the Add Variable button (+) to create a new collection variable.

Step 3: Enter a unique name for your variable in the Key field. For example, baseUrl or apiKey.

Step 4: Enter the initial value for your variable in the Value field. This could be a static string, numerical value, or even a complex data structure like an object or array.

Example:

Key: baseUrl
Value: https://api.example.com

2. Using Collection Variables in Requests

Step 1: Go to a specific request within your collection.

Step 2: In the request’s Authorization tab, select Bearer Token.

Step 3: In the “Token” field, type: {{apiKey}}

Step 4: Replace {{apiKey}} with the name of your collection variable.

Example:

{
  "url": "{{baseUrl}}/users",
  "method": "GET",
  "header": [
    {
      "key": "Authorization",
      "value": "Bearer {{apiKey}}"
    }
  ]
}

Step 5: You can also access collection variables within the request body using double curly braces: {{variableName}}.

Example:

{
  "name": "{{userName}}",
  "email": "{{userEmail}}"
}

3. Managing Collection Variables

3.1. Dynamically Setting Variables

You can dynamically update collection variables using Postman’s built-in scripting capabilities.

Example:

pm.collectionVariables.set("baseUrl", "https://staging-api.example.com");

This JavaScript code snippet updates the baseUrl collection variable dynamically based on your needs.

3.2. Scoping Collection Variables

Collection variables can be scoped to individual requests or the entire collection.

  • Request Level: You can define variables specific to a single request by using the Variables tab within the request’s interface.

  • Collection Level: Variables defined within the “Variables” tab of the collection itself are accessible by all requests within that collection.

3.3. Environment Variables

Postman allows you to define environment variables, which can be shared across multiple collections. This is useful for managing settings like test environments (e.g., development, staging, production).

Example:

Key: environment
Value: development

To access environment variables in your requests, use the {{environment}} syntax.

4. Best Practices for Using Collection Variables

  • Maintain Consistency: Use consistent naming conventions for your collection variables.
  • Keep It Organized: Organize your variables within different collections or environments to avoid clutter.
  • Use Data Files: Store large datasets or complex structures in external data files (JSON, CSV) and access them within your requests using the pm.variables.get() function.
  • Use Environment Variables for Global Data: Leverage environment variables to manage global settings like base URLs or API keys.

5. Conclusion

Collection variables in Postman are a fundamental part of effective API testing. By using this powerful feature, you can create robust, maintainable tests that adapt to changing API structures and environments. Leverage these techniques to enhance your API testing workflow, improve test efficiency, and ensure the quality of your APIs.

API Testing Blog