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On a multi-monitor system, if I'm viewing a full-screen video in Flash on one monitor, clicking the mouse on the other monitor causes Flash to leave full-screen mode and revert to normal size.

What's the easiest way of preventing this that works on my version of Flash?

My system is Flash 10 (, in Firefox 3.5 on Windows Vista 64, but I think it affects all current versions.

This is very annoying behaviour, but unfortunately, according to this bug report response it seem to be a security feature, rather than a bug:

We understand that many users would like fullscreen on one monitor and to be able to interact with your OS on another monitor. However, due to security requirements, we require that Flash and Browser must be the current focus of your OS.

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up vote 5 down vote accepted

Install Flash Game Maximizer Firefox plugin, maximize your Firefox window and press F12.

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Great, that works for me - I did find I had to select "Always Toggle Fullscreen" in the options. – therefromhere May 1 '10 at 14:00

Try running the browser + Flash in a VM that's capable of full-screen mode - VirtualBox is a popular, free option.

This is a fairly absurd workaround, but it looks like it should work, and this solution doesn't do anything to risk compromising security or breaking your machine.

On my machine it doesn't quite work though - I can switch Flash to fullscreen in the VM, but the video freezes as soon as I do so. However I think this is due to a graphics issue with my VM, since video is choppy on there anyway.

Please comment if this works for you!

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This issue would seem to be related to full-screen flash being bugged on Linux. – therefromhere Jan 3 '10 at 12:47

One of the comments in the linked bug report thread refers to this Youtube video (?!) giving the following instructions on how to hack the flash dll to workaround this.

NOTE: I know, this sounds like a REALLY BAD IDEA. I haven't tried this (my Flash dll is the wrong version), and it's quite possible that this may have nasty side effects such a introducing a security hole or breaking your system!

If nothing else, back up your dll before trying this.

That said, here's what the video says:

You need a hex editor and Flash player version or If you don't know what a hex editor is, cop out now.

  1. Open NPSWF32.dll - it's usually at C:\Windows\system32\macromedia\flash\NPSWF32.dll If you use Opera, it's probably at C:\Program Files\Opera\Program\Plugins\NPSWF32.dll
  2. Go to this hex address: Version 10: 0x136340 Version 9: 0xC1487
  3. If the number here is 74, change it to EB. If the number isn't 74, you've gone to wrong address, or you've got the wrong version of Flash, so these instructions won't work for you.

Please post in the comments if this works for you.

No abuse though if this causes your computer to catch fire or your dog to explode!

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You know any place that might throw in a free dog along with a new computer? – facepalmd Jul 30 '09 at 22:16

For youtube videos (or other services that have a similar embed feature). Simply click "Share" and "Embed". Grab the iframe URL (${video_id}) and navigate to that page. The video will use the full window, then fullscreen your browser.

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