To prevent unauthorized use of your API key, it’s highly recommended to restrict it to your website or server IP address. Follow these steps to apply restrictions:

Step 1: Open Google Cloud Developer Console

1. Visit Google Cloud Console and log in to your account.
2. Select the project associated with your API key.

Step 2: Access API Credentials

1. In the left-hand menu, go to “Credentials”.
2. Locate the API Key you created for the Spreadsheet Reader plugin.
3. Click on the API Key to edit its settings.

Step 3: Set Application Restrictions

1. Scroll down to the “Application restrictions” section.
2. Choose the appropriate restriction method:
   • Website restrictions (Recommended for WordPress sites): Only allow requests from specific website domains.
   • IP address restrictions: Limit API requests to your server’s IP.

Step 4: Add Allowed Websites (If Using Website Restrictions)

1. If you selected Website restrictions, click “ADD”.
2. Enter your website’s domain (e.g., yourwebsite.com).
3. Click “Save” to apply the restriction.

Step 5: Enable API Restrictions

1. Scroll down to “API restrictions”.
2. Select “Restrict key”.
3. From the dropdown, choose “Google Sheets API”.
4. Click “Save” to apply the settings.

Now, your API key will only work for requests from the specified sources, preventing misuse by unauthorized users.