You've seen streaming videos on YouTube and elsewhere, but every time you view them they use up some bandwidth and slow the internet down. There is no need for this, however, as these files do actually exist on your computer while you have YouTube displayed in your browser, and you are able to retrieve this file from your cache to keep forever.

How do I do that then?

Every page you visit on the internet goes into your browser cache, a limited amount of space on your computer's hard drive where everything you see gets stored temporarily; this is to save your browser having to fetch them every time you browse the same site, making your browsing experience faster even when you have broadband. All the images, pages, and video clips too, they're all there, but it's not as simple as all that because most browsers cache them in files without extensions and with random filenames. In this example I will show how to retrieve them using Firefox on the Mac, but I assume if you can find the same folders then the procedure should be much the same on all platforms.

First open the page with the video you want in Firefox, let it load completely, you don't have to play it, just so long as it's loaded and cached. Now look for your Firefox Cache folder - on the Mac it lives in ~/Library/Caches/Firefox/Profiles/ - at this point there should be a profile folder with a random name, something like '51tqw9jg.default' - the Cache folder is in there. Open the Cache folder and you should see several files with random filenames - look for one that is about 3MB or more in size (depending on the length of the video you're viewing on YouTube), copy this out to the Desktop or where ever and rename it something.flv (choose your own filename, but the extension must be .flv). This is your Flash Video file.

What now?

Either play it like it is, or convert it to a more portable format such as Quicktime. On the Mac I can import .flv files directly to Quicktime because I have installed the excellent Perian, "The Swiss Army Knife of Quicktime Components", after which I can save as a Quicktime .mov file without any trouble (Saving may require Quicktime Pro, can't remember if that option is there for standard Quicktime).

On other platforms you can use VLC, although it's not perfect (it creates green blobs for the first few seconds of video, no idea how to prevent this) but it works. Here's the procedure:

1. In VLC go to File -> Open File... and Browse for your .flv file (or type the location directly into the box)
2. Check the Streaming/Saving: check box and click Settings...

3. Ensure the File radio button is selected, then Browse for a target filename and location (or type it in directly to the box).

4. For Encapsulation Method choose Quicktime from the drop-down list.

5. In Transcoding options, check Video and choose h264 from the drop-down; also check Audio and choose mp4a.

6. You can specify Bitrates if you like, but I usually just leave those empty.

7. Click OK to go back to the Open File... dialogue, then click OK again to start the conversion.

8. If all is well you should see the progress bar moving along and the .flv filename in the VLC Controller, once it is finished your Quicktime .mov file is ready.

9. To convert further files simply go through to the Open File... dialogue again and change the source filename in the box next to the Browse button, then in Settings... change the target filename, click OK and you're good to go.

10. Remember to change the target filename otherwise your previous file will be overwritten without warning.

11. If you stop part-way through (using the VLC Controller stop button) the resulting file will be viewable up to that point.

One thing I'm not sure about is file sizes that get cached - I've had this strange thing where no file in the cache seems to grow beyond about 48MB, even though the video in the browser may be larger, I have no idea where the rest of the file lives (maybe in main memory?). This could be a Firefox limitation for cached files, altering the size of the cache in Firefox preferences makes no difference.

Feel free to send me or Ian any feedback on this page!