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 PCI compliance, upgrade to the latest version of Magento.

System 2.1 requirements

Our system requirements include required software to run the Magento application, supported web browsers, and also recent requirements to securely connect with our software repository and with PayPal.

See the following for more detail:

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