Downloading videos from YouTube

Guys, could you tell me if there is a convenient program for downloading videos from YouTube that allows you to choose the format and quality at once? Sometimes I need just audio, and sometimes I need full video for offline viewing. It would be great if the service supported conversion to different formats (MP3, MP4, AVI, etc.). What options do you know that work stably and quickly?

If you need a service to download and convert videos, the best option is Y2Mate. Here is the link to this youtube to mp3 converter . I had to look for such a site to work on video projects, and when on some forum a guy told me about Y2Mate, it just saved me! It is very convenient and fast, which is especially important when you work with a large volume of files. Now I only use it, and I recommend it to you too!