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Is there a tool or Firefox addon which could save already viewed video from YouTube?

I'm aware of services like KeepVid which downloads a video link. But I don't want to download again the video I have viewed using services like Keepvid.

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I think you should bold the "already viewed" part. Nobody seems to be catching on ;) – John T Aug 30 '09 at 17:21
If it is a long video, how about dowloading it first, and then watch it? That is what I like to do with long videos on places like YouTube anyways... =) – Svish Aug 31 '09 at 6:43
@Svish the only problem with that is, after watching some videos sometimes I don't like them after the first 10 seconds so im not forced to download any more and can leave the page. Downloading the entire thing every time would be a waste of bandwidth. – John T Aug 31 '09 at 6:51
Similar question here:… – Török Gábor Nov 12 '09 at 14:55

Since none of the answers really address your problem (or at least not correctly) I'll give it a go.

The browser caches youtube videos as Flash (.flv) although the extension is not apparent. With Internet Explorer, you can see the cache in Tools -> Internet Options -> Settings -> View Files. With Firefox you can type about:cache into the address bar, and under Disk Cache Device, click List Cache Entries. Viewing the files in Firefox makes it far less cryptic so you can determine the contents easier.

With IE an explorer window will open, you can simply sort the files by size or date modified, and look for files that start like this: videoplayback?ip= Use the timestamps to determine if it's the right one. You can simply copy that file to desktop and rename it with the .flv extension.

With Firefox on the disk cache page, press Ctrl + F to bring up the Find dialog and type in videoplayback, you should come to an entry in cache. Check timestamps to determine if the video is the right one, if it is click on it, if not click next in the find dialog until it is. There will be a link on the next page, right click it and select "save target as" and point it to your desktop. It should save instantly since the video is in your cache. Rename the extension to .flv if required. Since this process is a little extensive, here it is step by step:


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As far as programs and add-ons go, I don't think there currently is one for this.

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Please regard the comments for my answer. The file stored by flash isn't usable as flv. The first bytes of the file (identifying characters) are not that of flv. Do you know how to extract the flv out of this proprietary format? In any case, I believe the OP would prefer to re-download rather than go thru this excruciating process. – harrymc Aug 31 '09 at 15:06
It is flv they play fine. And the process isn't "excruciating", it just looks long typed out. It takes like 10 seconds. – John T Aug 31 '09 at 15:56
Unless you've just watched 20 of them and only want to save 2. Then you have to hunt them down, in which case I'd prefer a plugin. I think your answer is on the right track, though. – hyperslug Sep 1 '09 at 3:51
I think we'd all prefer a plugin, the thing is there isn't one right now. – John T Sep 1 '09 at 4:10

I'm afraid you can't reuse the viewed video, because it wasn't really downloaded. Such videos are streamed by the server and what you see in the browser is what is being streamed at the moment from the server site. Unlike images, the browser does not store videos in its cache.
Therefore you are obliged to re-download the video you have watched. There are many such downloaders available as FireFox extensions, just go to the extensions page and search for "video download".

Personally speaking, I prefer the video downloader installed by RealPlayer, which adds a Download button above the watched video and is real easy to use, doing everything in my own computer.

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Looks like a recent change now caches videos:…. When I close and reopen firefox, it doesn't redownload the video. – hyperslug Aug 30 '09 at 19:38
I checked it out, looking in Firefox at about:cache. I found that flash does save the video contents in the cache, but that the saved file seems to be in a proprietary format, neither flv nor swf. So, generally speaking, videos are still not stored in the cache in a useful format. – harrymc Aug 30 '09 at 20:07
it's flv – John T Aug 31 '09 at 3:13
I tried to rename the file to flv, but it wouldn't play. – harrymc Aug 31 '09 at 6:09
what are you trying to play it with?... – John T Aug 31 '09 at 16:00

On my Linux box with Firefox, I can do the following. Start playing the video on YouTube, wait until it pre-loads the whole content, then open /tmp folder, and there you find the video file in FLV format which you can immediately play with, for instance, MPlayer.

# /bin/ls -tr /tmp | grep  Flash
# cp /tmp/FlashLVBu97 ~/Desktop/some_video.flv
# mplayer ~/Desktop/some_video.flv
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I believe there is a Greasemonkey script which allows you to do that. I think it's this: .

GreaseMonkey in turn is an addon which allows or rather extends Firefox functionality a lot by allowing user-made "scripts" to customize pretty much anything in Firefox.

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Better YouTube by Gina Trapani at has an option that adds a download option to youtube. You may also consider DownloadHelper.

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+1 for downloadhelper a fabulous plugin – Nifle Aug 30 '09 at 17:49

I was looking for audio recording of streams and found Appian's Ask Toolbar which also does video saving.

The audio recording worked very well, though I haven't tried the video yet, so I don't know whether it copes with the already viewed part of your requirements.

Their blurb states:

This recorder is called the Ask & Record Toolbar and can record and convert video from 1000's of sites (including YouTube) and can save audio from ANY website.

It's not very intrusive and seems easy to uninstall so you could just give it a try.

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DownloadHelper is exactly what you need. This Firefox addon saves the already downloaded video from Youtube. -Just a happy user.

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was probably downvoted because download helper doesn't grab the video from cache but goes direct to server and starts over, something the OP doesn't want (or at least that used to be the case when I last tried DH) – matt wilkie Mar 26 '11 at 7:07

You can download video/audio with this software.


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