User Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:49.0) Gecko/20100101 Firefox/49.0 Build ID: 20160822111414 Steps to reproduce: disabled add ons (colorful tabs): no change Flush browser cache: no change reverted to earlier 49version, cleared problem over 200 tabs open Actual results: browser TAB BAR. web site Titles overlap adjacent tabs making titles unreadable, and tab borders are obscured, X to close tab, obscured too. reverting to earlier version cured situation. Expected results: Tab titles should be truncated to fit in tab space
This issue also happens with a clean profile?
I'm sure it won't happen with a clean profile, or it would have been noticed. But try it with 250 tabs open. My car also does not overheat, except when I drive it. If I leave it parked, it's just fine. Win 8.1 64bit os, 32bit firefox. Sorry to be snarky. Safe mode did not clear it up. I spent a couple hours alternating between between 2 computers to download an older version to get MY browser running the way it did before the "upgrade". Then I had to create a account to report a bug. I spent 20 years debugging software before I retired, so now I just report them.
I couldn't recreate it. What sites were overlapping?
User Agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:55.0) Gecko/20100101 Firefox/55.0 I have tested your issue on latest Firefox release v53.0 and latest Nightly (Build ID: 20170424030211) and could not reproduce it. I have opened 260 tabs some with webpages, some New Tabs but the titles did not overlapped and close button for tabs was clearly visible. Can you please try with the 64-bit Firefox version if you already have a 64bit OS? Is this still reproducible on your end ? If yes, can you please retest this using latest Firefox release and latest Nightly build (https://nightly.mozilla.org/) and report back the results ?
The problem seems to be caused by using older versions of the Tab Mix Plus extension. Installing the newest version fixed the problem for me.