I used this to convert music yesterday. Today suddenly AVG popped up with something called MalSign.BitCockTail.0e0 and several other things. I would avoid this. Also sometimes it would have a pop-up saying that your browser is out of date.
I have been using this webpage as a tool for 3 years now and have had no issues with it. It's not illegal because it isn't file sharing. They tried to make this against the law back then but they failed to make it a law.
This is an incredibly useful site. I use it to download Youtube videos that I don't really care about watching, just listening to, so that I can listen to them on the go. It protects you legally by keeping track of copyrighted material and if you inadvertently request some, gives an error message something like "Google doesn't want us to convert this video" so it's safe to use. The quality of the mp3s is perfectly adequate for anyone except the most horrible audiophile, but they probably wouldn't be using YouTube in the first place.
Best of all, Youtube-MP3 is free to use, is supported by non-intrusive advertising, and does not require its users to sign up or log in. More websites should be like this one.
There is the slight caveat, however, that it doesn't discriminate between regular and adult content, and will freely allow minors to access adult audio. This is the case even if SafeSearch is enabled on YouTube's website, should they obtain the URL to adult content. As with everything on the web, young children should be closely supervised when using this tool.
I've been able to convert a few videos, but all the other times I've gotten this.
"Google Inc. doesn't want you to convert this video.
Please sign a petition to change their mind:
Support third party recording tools for YouTube "