Video Downloader Professional/Plus - MPMux a browser extension for designed to save online videos for offline viewing
The developer states that the extension does not collect user data or store download history, with all processing occurring locally in the browser. Video Downloader Professional Plus - Mpmux Firefox
Note: Extension names and features may change over time. Always verify the latest version on Mozilla’s official add-on store. Video Downloader Professional Plus - Mpmux Firefox
Navigate to the page containing the video you want to save. The MPMux icon in your toolbar will typically change color or display a notification when it "sniffs" a media file. Video Downloader Professional Plus - Mpmux Firefox