You are extending your desktop on a second monitor and you want to play a full screen flash video, while working on the other monitor. If you use the other monitor the video will exit the full screen. Let's learn how to prevent this. Solution First we need to install GHex and use it to open libflashplayer.so ; open a terminal window and run: sudo apt-get install ghex -y && sudo updatedb && sudo ghex `locate libflashplayer.so` On GHex main window select Edit > Find and type _NET_ACTIVE_WINDOW . Click Find . Close the Find window and replace the N with an A : Save the file ( File > Save ) and restart your browser. NOTE: You will need to repeat this steps if flash gets updated. References UBUNTU MULTI-MONITOR TWEAKS (FULL SCREEN FLASH FIXES, SPAN WALLPAPER ACROSS MONITORS, MORE)
