Whenever (using flash) I make YouTube videos fullscreen then they come out not actually any bigger.

In the screenshot below you see exactly what I see when watching a video in fullscreen mode. All the black space shouldn't be there (I think). I don't see this problem in other sites, for example BBC iPlayer.

Screenshot of Flash YouTube on Ubuntu

Is this standard YouTube behaviour, common on YouTube, or is it just me?

Any suggestions on fixing it?

  • I've never seen this issue but you could try increasing the video resolution using the thing that says '480p' in the screenshot. Does this happen in all browsers?
    – dv3500ea
    Apr 24, 2011 at 18:16
  • I've seen a similar thing with multiple monitors; this machine only has one display, right? Apr 24, 2011 at 18:25
  • @dv3500ea No changing it didn't help.
    – 8128
    Apr 24, 2011 at 18:30
  • @Stefano No it has two displays, I should have mentioned that. I've just realised what was going on (ish) - see below
    – 8128
    Apr 24, 2011 at 18:30
  • @THeX No! Tis my friend...
    – 8128
    May 7, 2011 at 5:48

8 Answers 8


Okay, this is one of those embarassing occasions when you discover what's going on just after posting a question...

It is because of my dual monitor setup. YouTube is seeing the size of both monitors together, but then shrinks it to fit on one for some reason.

It doesn't happen on videos that are available in HD (in fact if the video is available in HD even if you watch it at 480p or lower resolutions then it works, which is a bit strange).

It seems this issue has been around for several years and the easiest fix is to enable HTML5 mode in YouTube.


I think the best solution is using the MaximizeFlash plugin for Chrome. It detects any flash in the page and you can make them fullscreen. To get rid of toolbar up just hit f11. You don't need to install any other apps.

For Firefox there is a similar plugin.


I have developed a workaround for this problem. It happens because Flash incorrectly determines the screen size when using multimonitor, so I coded a LD_PRELOAD hack that feeds Flash a different value when it asks for screen size. You can get it from my webpage:

Workaround for Flash on Linux Multihead Desktops | Al's Website

It's a bit tricky to install (you have to enter your screen size in the code and compile it yourself) but it does work.


The problem is flashplayer identifies your full screen as both monitors, and then scales it down to only one monitor so the video looks longer but smaller.

This drove me mad for months until I found this workaround found here:


Is basically a little script than "lies" to the browser modifying the environmental variables to make firefox think your fullscreen resolution is 1024x768 and not 2048x768 in my case (you can configure other resolutions) and use only one of both monitors. You need to install nspluginwrapper first (is in the repos).

Inside the .tar.gz you'll find the script and instructions to configure it. Also, instead of calling firefox with the parameters every time, you can make a little script like this I use and save it in your personal scripts directory (for instance $HOME/.scripts/firefox

LD_PRELOAD=/usr/lib/nspluginwrapper/i386/linux/libfullscreenhack.so /usr/bin/firefox "$@"

If you want to use the same with another browser like chrome or chromium you'll only need to do a similar script for them.

Good luck.

  • Thank you! So what exactly is causing the problem? Flashplayer or youtube? I've had this problem for literally years, it's things like this that hold linux back..
    – Tom
    May 6, 2012 at 13:09
  • @Tom: The problem is in flash player: the fullscreen window fill one output (a single monitor), but the video gets scaled as if that output had the resolution of the total display area (primary+secondary monitors)
    – MestreLion
    Jun 20, 2012 at 6:43
  • So the "boxed effect" you notice is actually a video with an aspect ratio of (1600+1024)x900 (roughly 2.91:1) resized to your 1600x900 monitor (1.78:1)
    – MestreLion
    Jun 20, 2012 at 6:45

I've have similar problems with a lot of apps like wine games etc. where the app is unable to detect the per-screen resolution and instead detects the total resolution as one screen.

The permanent solution i found was to run nvidia-settings , disable xinerama and configure "Seperate X Screen" . I now have two seperate displays , the usual DISPLAY=:0 and :0.1 . Since the X apps in both screen now run in thier own seperate sessions , with thier own desktop etc. , all apps detect the resolution for each monitor perfectly , and changing resolution in one screen does not affect another.

The only downside is i am unable to drag windows from one screen to another and need to launch apps in different screens as required. However this works perfectly for me since i keep browser in one display and the kids can play their emulator or see TV / movies on the other monitor without affecting my work.


Very easy workaround in Chromium / Chrome with Dual monitor set:

  1. Right click on the youtube video
  2. Select "Pop out"
  3. Now you have the video in a new window
  4. Move it to your second monitor
  5. Maximize the window
  6. Now you see the bar at the top
  7. For Video Controls, right click on video and select "Show Controls"

  8. Click on Full Screen Icon in the Video Controls
    OR Right click on the bar, select "Use System Title bar and Borders"

  9. The bar at the top disappeared
  • I think youtube removed the pop out option.
    – Anglepoise
    May 6, 2014 at 8:32

I have the same issue, having two different-resolution monitors connected to my PC.

My workaround is simple. Just zoom in in firefox until the video about fills the width of the screen. This also resolves another annoyance: if a video is playing fullscreen on one monitor, clicking on a window on the other monitor kicks the video out of fullscreen.


My workaround for this uses the data URL in Chrome to open an embedded video at the full screen resolution, then I put chrome in full screen mode. Try with:

data:text/html,<body style="background-color:black;">
<iframe width="1900" height="1060" src="http://www.youtube.com/embed/VIDEO_CODE_HERE" frameborder="0" allowfullscreen></iframe>

Just put the video code in and change the width and height to your screen resolution. Then put it in your address bar.

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