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# How to Fix Warning: "Prestashop _PS_MODE_DEV_ is active" - Amazon Marketplace Plus

When accessing the information page of the Amazon Marketplace Plus module, you may encounter the following diagnostic warning message:
> **Prestashop *PS\_MODE\_DEV* is active**
---

## Why Does This Warning Occur?

The `_PS_MODE_DEV_` constant is PrestaShop's native Development/Debug Mode setting. While highly valuable during website building or troubleshooting, leaving it **active** on a live production storefront introduces major issues:

1. **Severe Security Risk:** If any error occurs on your site, PrestaShop will display full technical details to your visitors, including your database structure, absolute server file paths, and vulnerable code lines.
2. **Performance Drop:** Debug mode prevents certain asset caching mechanisms, which slows down page loading times for your customers.
3. **Module Synchronization Failures:** Extra notices or warnings triggered in debug mode can leak into background AJAX/JSON payloads, breaking the module's automated connection with Amazon.

---

## How to Resolve the Warning

You can disable debug mode directly from your admin panel or manually via server files if the back office is inaccessible.

### Method 1: Disable Debug Mode via PrestaShop Back Office (Recommended)

This is the easiest and most common way to turn off debug mode:
1. Log into your PrestaShop back office.
2. In the left menu, navigate to **Advanced Parameters > Performance**.
3. Locate the **Debug mode** section near the top of the page.
4. Set the **Debug mode** toggle to **No**.
5. Click the **Save** button in the top right corner.

### Method 2: Update the Configuration File (Alternative via FTP)

If you cannot access your back office, you can disable it through your site's files:
1. Connect to your server using an FTP client or your hosting **File Manager**.
2. Navigate to the root directory of your PrestaShop installation.
3. Open the **`config`** folder and open the file named **`defines.inc.php`**.
4. Locate the following line of code (usually near line 28):
```php
define('_PS_MODE_DEV_', true);
```
5. Change its value from `true` to `false`:
```php
define('_PS_MODE_DEV_', false);
```
6. Save the file and upload it back to your server.