Update Checker

This is a custom update checker library for WordPress plugins and themes. It lets you add automatic update notifications and one-click upgrades to your commercial plugins, private themes, and so on. All you need to do is put your plugin/theme details in a JSON file, place the file on your server, and pass the URL to the library. The library periodically checks the URL to see if there’s a new version available and displays an update notification to the user if necessary.

From the users’ perspective, it works just like with plugins and themes hosted on WordPress.org. The update checker uses the default upgrade UI that is familiar to most WordPress users.

For more information anout this extra please refer to GitHub