Download YouTube videos without any Software: Google chrome trick
And unfortunately it is not available on the Chrome Web Store ... Google being subjected to pressure by the "rights holders" for strictly private copies.
But of course, there is always a solution :) Since you can easily download and install the Chrome extension Youtube Downloader via the website of the author.
When you install the extension, a very convenient "Download" button is added to all Youtube videos like the picture. And simply click on the button to download the video directly.
If you can first select the video quality (720p HD, 1800P), format (FLV or MP4) or even extract the sound mp3 of a Youtube video.