User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:2.0.1) Gecko/20110430 Firefox/4.0.1 Build Identifier: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:2.0.1) Gecko/20110430 Firefox/4.0.1 These pages have many images and use too much ram: http://www.militaryphotos.net/forums/showthread.php?99988-Russian-Photos-%28updated-on-regular-basis%29/page2737 http://www.mapcrunch.com/gallery http://www.9-eyes.com/ http://www.theatlantic.com/infocus/2011/03/air-strikes-on-libya/100031/ Comparison between browsers in terms of Private Working Set ram: Site FF x86 FF x64 IE x64 GC x86 http://www.mapcrunch.com/gallery 1.1 GiB 0.7 GiB 0.1 GiB 0.2 GiB http://www.militaryphotos.net/... 0.9 GiB 0.9 GiB 0.1 GiB 0.8 GiB -all four pages above- 2.1 GiB 0.3 GiB 1.2 GiB -25 mapcrunch pages- 6.9 GiB 1.1 GiB 2.0 GiB I know that tab memory is cleared after the tab has been idle for about a minute, but even while viewing the page the memory usage should be as small as in IE. Reproducible: Always Steps to Reproduce: Open the webpage Actual Results: Memory usage is high Expected Results: Memory usage should be low

Probably partly (or more) the same as bug 542158

Marking as depends on bug 542158 since I'm not certain this is a full dup

Bug 689623 improved this significantly. I just tested http://www.militaryphotos.net/forums/showthread.php?99988-Russian-Photos-%28updated-on-regular-basis%29/page2737. Before bug 689623, about:memory's "images/contents/used/uncompressed-heap" number was 249 MiB once the page finished loading, and it stayed there so long as you didn't leave the tab. After bug 689623, that same measurement peaked at 249 MiB immediately after loading, but then dropped to 30 MiB within about 20 seconds. When I scrolled to the bottom of the page quickly it jumped back up to ~249 MiB, and then again dropped, this time to 12 MiB, after about 20 seconds. The high memory consumption while scrolling quickly seems reasonable to me. The high memory consumption during page loading is sub-optimal, though.