Each website on a WordPress multisite network has its own media library and users cannot access media files uploaded from other website in a WordPress multisite network environ.
Although WordPress multisite network shares the codebase of core, themes and plugins but each media library is kept separate. In this lesson you will learn about sharing media files network wide so that you don’t have to upload same file on every website.
Network Shared Media plugin allows you to share media files across your WordPress multisite network so that files can also be used and access from other susbsites.
Start by installing ‘Network Shared Media’ plugin in WordPress
Upon network activation, the plugin automatically adds a new tab ‘Network Shared Media’ to the “Add Media” thick box. This new tab allows users to access media files of other blogs and websites hosted on your network.
Click ‘Network Shared Media’ and it will open up media files uploaded on other websites, you simply need to click ‘Show’ followed by ‘Insert into Post’ link.
One limitation of this plugin is that you cannot use images for generating post thumbnails i.e. featured images. Otherwise the plugin is good and works same as advertised.