I use Firefox to make screenshots (with pmview) on big virtual screens (with the old pmvdesk program which still works fine). So I get a window size of 6000 x 6000 pixels - this seems to be the current limit of Firefox 45. With Firefox 31 larger sizes were possible, 38 was more limited, too. If the window gets too large, Firefox vanishes without a comment. If it is an overflow problem, it should be fixed. If it is a memory problem, it is clear that fixing is not so easy.
I use Firefox to make screenshots (with pmview) on big virtual screens (with the old pmvdesk program which still works fine). So I get a window size of 6000 x 6000 pixels - this seems to be the current limit of Firefox 45. With Firefox 31 larger sizes were possible, 38 was more limited, too. If the window gets too large, Firefox vanishes without a comment. If it is an overflow problem, it should be fixed. If it is a memory problem, it is clear that fixing is not so easy.