If you are using a linux based operating system like Ubuntu, literally downloading the youtube videos is as easy as just watching it. I mean it when I said it. Anyway here I explain the best and the easiest options I found in downloading the youtube videos.
1.Just Watch the video.
One thing you would have rarely noticed is that when a video is buffered completely in Youtube, a copy of that video is saved in /tmp directory. So after watching the video make sure the you do not close or change the page in the browser. After the video is streamed fully in the browser just move to the /tmp directory and you can find a .flv file with name beginning with Flash*. Just copy that file into your desktop and it’s done. This is not the case with just youtube videos but any flash videos on net can be downloaded this way.
2.Command Line way.
If are comfortable with using command line, this way is for you. Youtube-dl is a Python script, which can run under Linux, Mac OS X, or Windows platforms as long a latest version of python is installed. For installing the script in Ubuntu just type
sudo apt-get install youtube-dl
Now for downloading a youtube video, in the terminal type
youtube-dl **video page url***
There are also a number of options available for you with this python script. You can view this by typing
youtube-dl –help
Options:
-h, –help print this help text and exit
-v, –version print program version and exit
-u USERNAME, –username=USERNAME
account username
-p PASSWORD, –password=PASSWORD
account password
-o FILE, –output=FILE
-q, –quiet activates quiet mode
-s, –simulate do not download video
-t, –title use title in file name
-l, –literal use literal title in file name
-n, –netrc use .netrc authentication data
-g, –get-url print final video URL only
-2, –title-too used with -g, print title too
-f FORMAT, –format=FORMAT
append &fmt=FORMAT to the URL
-b, –best-quality alias for -f 18
3. Grabber websites.
There are many websites like keepvid.com which allow users to download the youtube video by entering the url. But in many cases I have found this way do not work well.
4.Firefox plugins
If you are a Mozilla Firefox user there are a number of plugins which automatically detect any flash videos being played in the page. It need not be a ‘you’ tube page. This supports most of the other favourite websites. The below are just a few to name.
1-Click YouTube Video Download
Download Flash and Video
Flash Video Downloader
Fast YouTube Download
This is way I personally follow 
1) Also, another folder you can look into is the browser’s cache folder. You just have to look for large recent files, because they often won’t have any useful names or file extensions (but they can be renamed).
BTW, I haven’t had the problem with YouTube (because the files aren’t big enough), but I have had a problem with the /tmp folder and the cache folder not saving the entire video file with really big videos (specifically, I had a problem with videos over 60 MB). No matter what my cache was set to, the file would grow to 60 MB and just stop growing. I don’t stumble across too many .flv files larger than 60 MB, so it isn’t a problem normally.
4) I just wanted to throw my favorite Firefox addon into the ring: Video DownloadHelper (https://addons.mozilla.org/en-US/firefox/addon/3006) I found it after having trouble with an .flv file that was larger than 60 MB.
Thanks for sharing.I will be adding the addon to my list.
I have never had a problem with just opening /tmp then waiting for the OS to make a tumbnail for the file.
The just drag it somewhere else and watch it.
I need that Video DownloadHelper on OSX though.
Few days after publishing this post I came across a news that certain videos when dowloaded by copying from /tmp actually do not work. I think it is due to some kind of encoding or something else. So I am just thinking if that method becomes successful always .
I love youtube but it does have some bad things on it. Like with copyright and things.
Nice blog, I envy it, but it looks a little out of layer while using mozzila browser, keep it moving:)
thank you very much for the information. i am a beginner to ubuntu and i have been searching fr some time for a simpler solution. Now i can save my favourite videos in no time. i am in Mozambique and in a short time i have become a geek. thanks
it’s great we have readers even from mozambique.
best wishes