diff -u b/src/Controller/S3CorsUploadAjaxController.php b/src/Controller/S3CorsUploadAjaxController.php
--- b/src/Controller/S3CorsUploadAjaxController.php
+++ b/src/Controller/S3CorsUploadAjaxController.php
@@ -79,11 +79,8 @@
       ['acl' => $post['acl']],
       ['bucket' => $bucket],
       ['starts-with', '$key', $destination . '/'],
-      ['Content-Disposition' => 'attachment; filename="' . $post['filename'] . '"'],
     ];
 
-    $post['Content-Disposition'] = 'attachment; filename="' . $post['filename'] . '"';
-
     // Retrieve the file name and build the URI.
     // Destination does not contain a prefix as it is applied by the fly system.
     $uri = \Drupal::service('file_system')->createFilename($post['filename'], $post['destination']);
@@ -99,6 +96,20 @@
     ]);
     $file->save();
 
+    // Set file mime so browser would know how to handle them eg images are
+    // shown not downloaded.
+    $file_mime = $file->getMimeType();
+    $options[]['Content-Type'] = $file_mime;
+    $post['Content-Type'] = $file_mime;
+
+    // For downloadable files always download with original name.
+    // @todo: Is 'application/*' mime enough?
+    if (strpos($file_mime, 'application/') === 0) {
+      $content_disposition = 'attachment; filename="' . $post['filename'] . '"';
+      $options[]['Content-Disposition'] = $content_disposition;
+      $post['Content-Disposition'] = $content_disposition;
+    }
+
     // Remove values not necessary for the request to Amazon.
     unset($post['destination']);
     unset($post['filename']);