---
title: "Parameterize your script for multiple environments | Grafana Labs"
description: "Use environment variables to make your k6 script portable across dev, staging, and production without code changes."
---

> For a curated documentation index, see [llms.txt](/llms.txt). For the complete documentation index, see [llms-full.txt](/llms-full.txt).

# Parameterize your script for multiple environments

A CI/CD pipeline often runs the same script against different environments: a preview after a pull request, staging before a release, and sometimes production after deployment. If your script has a hardcoded URL, you need a separate script for each environment. Environment variables eliminate this problem. You define the target URL once as a variable and pass the value at runtime.

To parameterize your script, complete the following steps:

1. Open your k6 test script and replace any hardcoded URLs with `__ENV.BASE_URL`. For example, change:
   
   JavaScript ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy
   
   ```javascript
   const res = http.get('https://staging.example.com/api/health');
   ```
   
   to:
   
   JavaScript ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy
   
   ```javascript
   const res = http.get(`${__ENV.BASE_URL}/api/health`);
   ```
   
   `__ENV` is a k6 global object that provides access to environment variables passed with the `-e` / `--env` flag or set in the shell environment. For details, refer to [Environment variables](/docs/k6/latest/using-k6/environment-variables/).
2. Run the script locally with the `-e` flag to pass the base URL:
   
   Bash ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy
   
   ```bash
   k6 run -e BASE_URL=https://staging.example.com test.js
   ```
   
   Verify that the test runs successfully against the specified environment.
3. Add a default value check at the top of your script to catch missing variables early:
   
   JavaScript ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy
   
   ```javascript
   const BASE_URL = __ENV.BASE_URL;
   if (!BASE_URL) {
     throw new Error(
       'BASE_URL environment variable is required. Use: k6 run -e BASE_URL=https://... test.js'
     );
   }
   ```
   
   Without this check, a missing `BASE_URL` produces confusing HTTP errors instead of a clear message about the missing variable.
4. Test that the error message works by running without the `-e` flag:
   
   Bash ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy
   
   ```bash
   k6 run test.js
   ```
   
   You should see the error message you defined. This confirms that the script fails fast when the required variable is missing.

> **Tip:** You can parameterize more than just the URL. Use `__ENV` for any value that varies between environments, such as authentication tokens (`__ENV.API_TOKEN`). Keep secrets out of the script and inject them from your CI platform’s secret store.

In the next milestone, you add k6 as a step in your CI/CD pipeline.