While people have brought up video grabbers for YouTube are a dime a dozen, no one's brought up a general video grabber so I'd like to recommend
Video Downloadhelper.
https://www.downloadhelper.net/
https://addons.mozilla.org/en-US/firefox/addon/video-downloadhelper/
https://chrome.google.com/webstore/detail/video-downloadhelper/lmjnegcaeklhafolokijcfjliaokphfk
It's kind of shit at YouTube, but it's great for getting shit behind an HTML5 player or hidden from downloading by other means.
Videos and music download quickly as long as the site itself doesn't throttle connections, IIRC it downloads files simultaneously in multiple chunks to speed up downloads. (Says it supports "media" in flv/ram/mpg/mpeg/avi/rm/wmv/mov/asf/mp3/rar/movie/divx/rbs/mp4/mpeg4 formats but I'm pretty sure it can pull sfw and ogg/ogv as well.) Also displays the size of available media so you know what you're looking for. All in the convenience of an extension
Can't remember if it was for both Chrome and Firefox, but ever since Mozilla took away some feature when they pushed Quantum, it requires a companion app to get files that are too big for the browser to handle, but the app runs completely in the background and doesn't have any noticeable performance impact when it's doing it's thing.
Only real downsides I've noticed are it can't get content that's live streamed (like Soundcloud or an active Twitch stream, archived streams are fine), it has a length limit at 3 hours or so (it saves the middle of the video for some reason), and the fact it's slow as shit at pulling videos off YouTube, then plexes the video with a QR code to say "hey, buy our software." Apparently you can use a converter feature if you pay for it, but just use Any Video Converter like a normal fucking human being.
The price is fucking ridiculous ($28.50 or 18.50 euro, though granted it is a one time payment), but they exclusively process payments through Stripe, so even someone like Dear Leader could pay for it.