Dropzone library makes it easier to implement file upload using drag and drop on the page.
After file uploading, it shows the preview of the file in the upload area.
All the thumbnails are removed when the webpage is getting refreshed.
To recreate the thumbnails after page refresh needs to send AJAX request to get all files list for adding thumbnails while initializing Dropzone.
In this tutorial, I show how you can display existing files stored on the server in the Dropzone file area with jQuery AJAX.