Browsing videos on YouTube is great fun, but what happens when you find one you'd like to view offline, keep or transfer? Although you can embed or link to videos you like, YouTube doesn't actually give you any option to download them. Don't worry, because some of Firefox's great add-ons (plugins that you can use to extend your browser) can do the job for you, all without even having to open a second program. Let's take a quick look at some of the best.

YouTube Video Downloader does exactly what it says on the tin. The 'keep' icon, located in the status bar, opens the video details in a new tab, prompts you to chose a format (FLV, 3GP or MP4), name the video and download it. That's it! Easy, right?

Another discreet option is Easy YouTube Video Downloader - it simply adds a button underneath the information displayed to the right of YouTube videos. Like its predecessor, it supports FLV, 3GP and MP4, but without the new tab is possibly even simpler to use.

NetVideoHunter takes a different approach, opening a window containing a list of the videos you have been viewing. The main selling point is that it 'collects' videos as you browse them. At the end of your session, it presents you with a list of the videos you have just seen, allowing you to pick the ones you want to download. It also has the added advantage of being able to download from video sharing sites apart from YouTube, such as Dailymotion and Google Video, and includes a player, so you can view videos even after you have closed the original page.

If you are looking for a little excitement, try YouTube Downloader. This experimental add-on is so thrilling that you have to check a box to say that you understand the risks - although when I tested it, it didn't seem too wild. Youtube Downloader lets you download videos and music, and not just from YouTube. Like NetVideoHunter, it presents you with a list of possible downloads, and then lets you select the ones you want. It also has a search function which will automatically search for the video title on Google.

If discretion's not your thing, maybe the Ant.com Toolbar - Tube Downloader is what you are looking for. Although it does install a toolbar on your browser, it's only to accommodate the extra options it includes - a search tool, download manager, video player, download explorer and a ranking function. It is also more customizable than some of its competitors, allowing you to toggle a small number of options.

Whether you're a dedicated video downloader or just someone who browses occasionally, you'll find an add-on to suit. Read the reviews, make your decision and start downloading videos from YouTube today!