User Agent: Mozilla/5.0 (Windows NT 6.1; rv:36.0) Gecko/20100101 Firefox/36.0 Build ID: 20150305021524 Steps to reproduce: I use a javascript statement like this to display (larger) images: this.display.style.backgroundImage = 'url(\'' + imageUrl + '\')'; In combination with window.setTimeout this is used as a slide show. (Advantage: with css "background-size: contain" I don't have to care about image proportions) Actual results: With each background change firefox memory usage increases substantially - even if images have been shown already. Reaches about a Giga. After a while images are not displayed anymore. Console log says Images corrupted / truncated. Firefox does free Memory when switching tabs inbetween. Firefox 36.0.1 Windows 7 ultimate 32 Bit Service Pack 1 Expected results: Memory must be freed continuously without having to switch tabs inbetween. (Chrome, IE do not increase memory usage, opera does, but obviously applies a garbage collection every once in a while)

Forgot to remark: there haven't been any add-ons active.

Could you attach a testcase to show the issue up, please? In addition, if you're able to reproduce the issue with a fresh profile (see https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles), could you save and attach a memory log from the page about:memory.

FF keeps in memory all the decoded images, so that's why the memory use is growing up fastly. Is it by purpose?

tn, can you comment on this?

For background images (and other CSS images) we currently don't make any attempt to get rid of images that might be unused. We have bug 1042393 for this.