## Troubleshoot Environment Variables

Find suggested solutions for common errors while working with environment variables.

### PUBLIC\_\_ variable not available in client code.

Your client-side code can't access a variable that you prefixed with PUBLIC\_\_.

**Cause:** A single underscore or missing prefix means the variable is treated as server-only.

**Suggested Solution:** Verify the variable name starts with PUBLIC\_\_ (two underscores).

### Config path error on startup.

Your app fails to start and displays a config path error.

**Cause:** The path in your PUBLIC\_\_ variable name isn't found in config.server.ts.

**Suggested Solution:** The path in your PUBLIC\_\_ variable name must exist in config.server.ts. Add the field and its default value to the config before setting the environment variable.

### Environment Variable Isn’t Set

Your code throws an `Error` stating that a variable is missing.

**Cause:** The environment variable that the code calls isn’t set.

**Suggested Solution:** Call the [projects_target_env_var_partial_update](https://developer.salesforce.com/docs/commerce/pwa-kit-managed-runtime/references/mrt-admin?meta=projects_target_env_var_partial_update) API endpoint to set the applicable environment variable.

### Incorrect Environment Variable Name

Your code logs an error message stating that the environment variable wasn’t found.

**Cause:** The code couldn’t find the environment variable because of a typo or incorrect variable name.

**Suggested Solution:** Confirm that you spelled the environment variable name correctly and that you’re using the right name. To see all set variables, call the [projects_target_env_var_list](https://developer.salesforce.com/docs/commerce/pwa-kit-managed-runtime/references/mrt-admin?meta=projects_target_env_var_list) API endpoint.

### Unsupported Environment Variable Name

Your API call to set an environment variable fails.

**Cause:** The environment variable name doesn’t comply with the [constraints](/docs/commerce/b2c-commerce/guide/sfnext-mrt-environment-vars.md#constraints). For example, the variable value exceeds 32 KB.

**Suggested Solution:** Confirm that your environment variable complies with the [constraints](/docs/commerce/b2c-commerce/guide/sfnext-mrt-environment-vars.md#constraints).

### Invalid API Key Format

Authentication errors occur when you execute code that uses an API key.

**Cause:** The API key that you used when you set the environment variable isn’t in the expected format or is missing.

**Suggested Solution:** Confirm that the API key stored by an environment variable is correct. If needed, call the [projects_target_env_var_partial_update](https://developer.salesforce.com/docs/commerce/pwa-kit-managed-runtime/references/mrt-admin?meta=projects_target_env_var_partial_update) API endpoint to correct the API key.

### Invalid URL for an API Endpoint

A `fetch` request fails with a network error.

**Cause:** A URL for an API endpoint in your code is missing or invalid. For example, the URL for a content management system (CMS) endpoint is incorrect.

**Suggested Solution:** Confirm that any URLs for API endpoints in your code are correct.

### Variable Has No Effect After Being Set

**Cause:** Environment variables load at startup. A running server doesn't pick up changes automatically.

**Suggested Solution:** Restart your dev server.

### `PUBLIC__` Variable Not Available in Client Code

**Cause:** A single underscore or missing prefix marks the variable as server-only.

**Suggested Solution:** Verify that the variable name starts with `PUBLIC__` (two underscores).

### Config Path Error on Startup

**Cause:** The path in your `PUBLIC__` variable name isn't found in `config.server.ts`.

**Suggested Solution:** Add the path and its default value to `config.server.ts` before setting the environment variable.

### Variable Value Is the Wrong Type

**Cause:** The variable value isn't formatted correctly for its type. The app parses values automatically.

**Suggested Solution:** For booleans, use the string true or false. For arrays and objects, use valid JSON. Confirm the value is formatted correctly in your .env file or in Runtime Admin.

### API Call to Update Variables Fails

**Cause:** This error can be caused by insufficient permissions, an invalid API key, or a reserved prefix.

**Suggested Solution:** Confirm that you have the developer or admin role on the project. Verify that your MRT API key is valid. Check that the variable name doesn't use a reserved prefix.

### Variable Set in Runtime Admin Is Not Available After Deployment

**Cause:** You likely didn't deploy the bundle after setting the variable.

**Suggested Solution:** Make sure that you deployed your bundle after setting the variable. Existing running instances use the variables that were active at deploy time.