About the youtube video downloader
Most searches for a YouTube video downloader end in the same place: the person actually wanted several videos, from the same channel or the same series, and only started with one. That is why this site is organised around lists rather than single URLs — the single case is a list of one, and the multi case does not require a different tool.
The mechanics are worth understanding. YouTube serves video and audio as separate streams at higher resolutions, which is why some tools quietly cap at 720p — that is the highest resolution still available as a single combined stream. Anything above it requires the two streams to be merged, and that is a server-side job, not something a browser tab can do on its own.
Format choice is the same decision as everywhere else on this site. MP4 for anything visual, MP3 or M4A for anything you only listen to. Choose once per batch, not per file, and your library stays coherent.
Be sceptical of any downloader that asks you to sign in with a Google account, install an executable, or disable your antivirus. None of those steps are required to read a public video's available streams, and each one has an obvious downside if the site is not what it claims to be.
Finally, the legal shape of this: downloading is a tool, and how you use it decides whether it is reasonable. Keeping a copy of a lecture you can already watch for free, so you can study it on a train, is a different act from re-uploading someone's work or selling it. Respect the creator's licence and the platform's terms.