Take the 2-minute tour ×  This has happened for me as long as I
can remember. Since the first version of Firefox, on multiple
computers and under different versions of Windows. QuickTime
plays fine in IE and Chrome (even with Firefox in the
background), but in Firefox if my mouse is not over the
QuickTime window then it will start to studder, then lag and
eventually just stop.    • To be honest, I do keep quite a few
tabs open, but Firefox stays at 1% CPU (even when QuickTime
runs) and I have a few gigs of free RAM.   • It is the same for
any resolution of video or audio.   • If the mouse is just one
pixel in the client area of the QuickTime then it usually plays
fine.   • Other video formats typically play fine.  Does anyone
else notice this behavior? Ultimately I would like a fix besides
keeping my mouse over the QuickTime window.  share|improve this
question add comment  1 Answer  Most video lag in Firefox is
caused by the session saving feature. Here is the fix (which
will work for YouTube, Hulu and other