You run a WordPress Multisite installation and want to share files in your media library between multiple sites? We explain why this is not the case by default and why it is a bad idea to do this with a plugin.
Why are the media libraries seperated?
WordPress itself does not support “shared” elements (posts, media, etc.) in a multisite installation. A multisite installation is meant to allow multiple WordPress websites to be located in one technical installation. However, these websites should be able to be operated by different administrators or even organizations.
Therefore, it is a design decision by WordPress not to use a media sharing mechanism between your sites. Files from multiple sites and possibly organizations should never be mixed, as there may be confidential data among them. Each site in a multisite should be isolated and work without other dependencies.
If the individual sites were not isolated, this would also lead to technical conflicts when you try to migrate the site out of the WordPress Multisite at a later time.
There are plugins like shared-media-library that allow you to use a shared media library for all websites in a WordPress Multisite. Plugins like these interfere with the fundamental design of the WordPress core, which was not built for such a purpose. For example, the upload rights management in WordPress is very rudimentary, which makes it impossible to implement important restrictions in a shared media library. In addition, plugins like the one mentioned above must introduce their own APIs, to which plugins like Real Media Library can often be incompatible. Compatibility issues and corresponding malfunctions with other plugins and your theme may occur.