The original 2017 Blu-ray remains the absolute highest quality (less compression, higher bitrate), but a 2021 Web-DL is often preferred for its smaller file size while retaining near-Blu-ray transparency.
WEB-DL 2021" refers to a specific of the 2017 Michael Bay film that likely became available or was updated on streaming platforms like Prime Video or Netflix in 2021 . Movie Background transformers the last knight 2017 web dl 2021