We have a setup running on RedHat Enterprise Linux 6 and Firefox (52.8.0 ESR from RedHat). We use thin clients running RHEL 6 and XDMCP to run Firefox on a main "server" (also running RHEL 6). When doing something that requires high refresh rates, such as watching video or using a map (Leaflet.js) the input is delayed (sometimes takes several seconds just to pause the video). The problem is exacerbated by more clients. Having more than 5 clients makes it nearly unusable. Notes: The issue seems to appear with versions after Firefox 45.7.0 (which came with RHEL 6.9). I haven't tried every Firefox version, but definitely appears in 52.4, 52.6, 52.7.2 and 52.8. Chromium does not have the same issue. Our issue is not over SSH: https://unix.stackexchange.com/questions/187415/why-is-firefox-so-slow-over-ssh gfx.xrender.enabled improves the performance, but is still much slower than v45. https://www.reddit.com/r/firefox/comments/4nfmvp/ff_47_unbearable_slow_over_remote_x11/ I know RHEL 7 is out, but preliminary tests looks like it doesn't fix the issue. I know XDMCP is an old protocol. It is not an option to change it yet. Has anyone else experienced this specific issue? If so, are there any plans to fix it? If this has not been reported, I can provide more info on how to reproduce it.