User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:51.0) Gecko/20100101 Firefox/51.0 Build ID: 20170125094131 Steps to reproduce: I use ScreenToGIF program — https://github.com/NickeManarin/ScreenToGif — for GIF recording. I record any GIF → I edit GIF → I save GIF in «ScreenToGIF» encoder. http://i.imgur.com/FuhT3V6.png I upload my GIF to any hosting. GIF examples: http://i.imgur.com/wQwsoWR.gif http://i.imgur.com/vCgnTpa.gif Actual results: GIF not displayed in Firefox, I get error: > image cannot be displayed because it contains errors See more details here: https://github.com/NickeManarin/ScreenToGif/issues/79#issuecomment-278311421 Expected results: Successfully GIF displayed. The problem reproduced for me in Safe Mode in Firefox 51.0.1 (64-bit). The problem not reproduced for me in: Chrome Version 56.0.2924.87 (64-bit), Opera 38.0.2220.41, Internet Explorer 11.576.14393.0. I have a problem only in Firefox.

Fixed by bug 1258741. https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=7362a3b3d23989a2ced1ffd112a66ec300c77e40&tochange=d56e9b123ed63993592c477540b64ec24a18002b