I am looking for a solution that would allow me to save online videos, especially YouTube, to the iPad for later offline viewing.
Safari and Chrome
I had no luck getting any extensions working. YouTube intercepts right clicks on video and shows a youtube context menu instead of the native context menu and thereby blocking the download button.
Download YouTube Videos as MP4 and FLV 1.3.8 is an extensions which is compatible with Firefox 11 (as of march 2012). It shows a download button below the Youtube video area.
The download format is
.mp4 which is fine to use on an iPad.
Still, if you want to convert the downloaded video for your mobile devices, you can use a simple tool like the MiroVideoConverter, which is available in the Mac App Store for free.
Check out Zamzar, which allows you to enter the URL of a YouTube movie and translated it to, for example, MP4, which can then be added to your iTunes library and synced to your iPad. Once the translation has finished, you'll get an email with a link to download the new file.
Most solutions I found on the net were not working anymore but I found this Safari extension that worked just fine https://github.com/jonathanboom/YouTube-video-downloader-for-Safari