Manual:$wgCopyUploadsFromSpecialUpload

Details
By default, upload by URL, when enabled via  , is only possible using the upload>Special:MyLanguage/API:Upload|API (or extensions such as ext>Special:MyLanguage/Extension:UploadWizard|UploadWizard). To make the option usable from Special:Upload, you can set this variable to true.

In order to make use of this option, users also need to have the option   set to true and the associated 2>Special:MyLanguage/Manual:$wgGroupPermissions|user right.

Example usage
This example setup will allow all autoconfirmed users to upload by URL, via Special:Upload or the API. Add to the bottom of your :