Most tube sites explicitly state in their Terms of Service that downloading content without permission is prohibited.

Tools like 4K Video Downloader or browser extensions allow users to save files directly to their hard drives in formats like MP4. While popular for saving tutorials or creative assets, users must be cautious of copyright laws and the security risks associated with unverified software. The Ethics and Legality of Downloading

Popular options include "Video DownloadHelper" (for Firefox and Chrome) or various "Media Downloader" add-ons.

: Be aware of the copyright laws in your country. Downloading copyrighted material without permission is illegal in many places.