As per the new report whatsApp is testing a new feature that will show the full preview of videos and images that are shared as documents on the Android app,
called ‘Document Preview'. This will show a large preview of the content sent over the Meta-owned app. This preview feature currently available for PDF files.
WhatsApp usually compresses the videos and images sent over the messaging app, forcing the users to send images as documents to retain the content's original quality.