- Finding a reliable one that stays up for long is a challenge.
- Most of them are riddled with ads.
- Not all video resolutions are available on them because some formats(especially 1080p & above) stream the audio separately, and would need to be merged after downloading.
- If any website allows you to download the above formats, it's doing the merging server side. And there's a very high chance that server's using youtube-dl.