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.

Package

Use Composer to package your module.

Using Composer to package a Magento 2 module
Use our validation tool to check your package before you distribute it.
Distribution on Magento Marketplace only. Upload your package to the Magento Marketplace

May 31st, 2019