Magento 2.1.x Notice: Magento 2.1.18 is the final 2.1.x release. After June 2019, Magento 2.1.x will no longer receive security patches, quality fixes, or documentation updates. To maintain your site's performance, security, and PCIPayment Card Industry: Refers to debit and credit cards and their associated businesses. compliance, upgrade to the latest version of Magento. The Magento User Guide 2.1.x remains available in PDF for Open Source and Commerce.
Use the Advanced Developer tools to determine the compilation mode during frontend development, create a whitelist of IP addresses, display template path hints, and make spot changes to text in the interface of the storefront and AdminThe password-protected back office of your store where orders, catalog, content, and configurations are managed..