Restrict uploads file types

Is it possible to restrict uploads file types for selected WordPress role? Thanks to WordPress developers, Yes.
There is a special Upload Mimes Filter ‘upload_mimes’, which allows to change what file types are allowed to upload to your WordPress.
Let’s use the example when we need to allow to ‘author’ role upload/attach to the posts just PDF files.
Your steps are simple:
1) create .php file, e.g. myme_types.php;
2) insert this code there:

add_filter('upload_mimes','restrict_mimes_for_author');
function restrict_mimes_for_author($mimes) {
  if (!current_user_can('author')) {
    return;
  }
 
  $mimes = array('pdf' => 'application/pdf');
 
  return $mimes;
}

3) Save changes and place this file to the wp-content/mu-plugins folder.

Thats’ it. Now, in case your author try to upload any file type except PDF he will get this error message from WordPress:

You may download ready to use file myme_types.php here.

If you need to extend allowed file types, add them to the $mimes array above as additional elements. For example, to restrict uploads file types to PDF and JPEG only, use this array:

$mimes = array(
'pdf' => 'application/pdf',
'jpg|jpeg' => 'image/jpeg'
);

The list of mime types is available here.