Originally posted on Stack Overflow: https://stackoverflow.com/questions/59320473/stackoverflow-duplicated-layer-bug

Requirements to reproduce:

Windows 7 x64
Firefox 71.0 x64

Steps to reproduce:

  1. Go to the ask question section
  2. Write something to the title field
  3. Start scrolling similar questions
  4. Change the title field
  5. Start scrolling the similar questions again

The look you will get

  • The original MSO bug report is here. Also re-reported here: meta.stackoverflow.com/questions/392102/… Commented Dec 13, 2019 at 19:17
  • I can confirm this bug when StackExchange sites are opened in Firefox 72.0.1, which as of this comment, is the latest general release. I have not seen this issue on any other websites. My temporary solution is to use a content blocker to block the 'Similar questions' area until it is fixed. Hopefully someone at SE will let us know if this is being worked on. Commented Jan 14, 2020 at 0:14
  • 1
    Still a problem in Firefox 73.0 (Windows)
    – MrWhite
    Commented Feb 13, 2020 at 12:32
  • @RockPaperLizard "temporary solution is to use a content blocker" - How is that a "solution" of any kind? (Why not just ignore it? It's not a problem until you start to interact with it.) But you can temporarily "fix it" by just closing/opening the "Similar questions" dropdown. Or even just clicking off the "Similar questions" area and clicking back (although that is a bit hit & miss).
    – MrWhite
    Commented Feb 13, 2020 at 12:51
  • @MrWhite You chose to leave out a key word when quoting what I wrote. I wrote "My temporary solution...". I prefer not to have a large UI element that does not work properly cluttering the page, and so MY solution is to remove it until it is no longer broken. Commented Feb 14, 2020 at 7:45
  • 1
    I'm facing the same behaviour on Firefox 75.0 (64-bit) on Ubuntu 18.04. A workaround is to click twice the little up-arrow ^ at the top right of the affected component to make this bug disappear (at least temporarily).
    – s.k
    Commented Apr 13, 2020 at 8:25
  • 1
    Still happening Firefox 75.0 64-bit Windows 10 build 18363. Please fix.
    – rory.ap
    Commented Apr 23, 2020 at 12:41
  • Also reported on MSO 2020-05-04. Two combinations: Firefox 75 (current for the date) and Ubuntu 19.10 (Eoan Ermine) / Ubuntu 20.04. It may or may not be an intermittent problem. Commented May 4, 2020 at 16:12
  • 1
    FF79/Ubuntu: still problem. What a PITA this is, 9 months on from this being raised (and raised again). I don't think SO have got their priorities right in terms on UX development at all. Commented Jul 2, 2020 at 7:09
  • Is anyone able to repro right now? I am unable to repro on Win 64, Firefox 85 or 86. Commented Mar 21, 2021 at 19:51
  • I can't reproduce it now on firefox 86, win10 x64. Maybe it's solved. Commented Mar 23, 2021 at 16:39

8 Answers 8


I am able to reproduce this running Firefox 68.3.0 ESR on macOS v10.14.6 (Mojave):

Enter image description here

It appears that it is the exact same layer duplicated over one another.


A couple of notes I made while testing (Firefox 71 on Windows 10):

  1. I can only make this happen if I'm zoomed in
  2. I can only make this happen on Firefox
  3. The artifact disappears if I switch tabs or even just hide the Firefox window briefly
  4. If I turn off the clip-path style on #js-similar-questions-expandable, this stops happening entirely.

My gut feeling here is that this is a Firefox bug, although one we could possibly work around at the cost of making collapsing that list look a bit more ugly.

  • 1
    Shog, 3 I concur, 1 I have to disagree. For me it works on 100% zoom
    – Luuklag
    Commented Dec 13, 2019 at 18:25
  • @Luuklag Do you by any chance happen to be using a high-DPI screen? Commented Dec 13, 2019 at 18:28
  • Cant recall if I tested it on external monitor or not. Otherwise on a macbook air 2018. External monitor is a dell from this year, widescreen. @SonictheReinstateMonica-hog
    – Luuklag
    Commented Dec 13, 2019 at 18:54
  • Although there is currently no data to conclude it's a Firefox bug, if it turns out to be one, please report at bugzilla.mozilla.org Commented Jan 14, 2020 at 0:17
  • I'm on Firefox 77 on Windows 10. This is still an issue.
    – LShaver
    Commented Jun 24, 2020 at 13:16
  • Speaking about zoomed in, in my case I can make this bug visible by going into Full Screen Mode (F11) or when switching back to it. Commented Sep 8, 2020 at 9:59

I'm seeing this in Firefox 71.0 on macOS 10.13.6 posting this question:

enter image description here

The effect appears whenever I edit the question title. It disappears whenever I interact with the page in any other way (e.g. clicking on the page or leaving the browser window).


I have the same problem since months and I wanted to do a report myself but never found the time to.

The possible duplicate suggestions blend with each other when scrolling through them. If you do not scroll they don't blend.

To be more precise, the suggestion which is on top persists while the following question scrolls up. The result is that both more or less fixed stand on the same place.

I found out that the problem occurs especially when swapping Firefox to full screen mode (F11) or out of full screen mode.


  • Browser: Firefox 80.0.1 64-bit
  • OS: Windows 10 Home 64-bit


Screenshot 1: SS1

Screenshot 2: SS2

Screenshot 3: SS3


I'm going to close this as , not because it wasn't reproducible, because all these answers and comments clearly show it was, but because it appears to have resolved sometime after February 2021 or Firefox 85.

Based on everything we've seen, I suspect our magical CSS expand/collapse code was hitting a sharp edge in Firefox where it cached a rendered snapshot of the element around and rendered it underneath the live HTML.


I am also facing the same issue ever time while posting a question.

  • Firefox: 80.0.1 (64 Bit)
  • OS: Windows 7 64 Bit

And the observation is, before scrolling into "Similar Questions", if scroll the entire page a little bit and then performs scroll in "Similar Questions" section does not create any issue of overlapped styling.

enter image description here


I am also having the same issue. It appears to me first on Chemistry but I could replicate it on Meta as well. The problem appears when asking a new question.

How to reproduce

  1. Type a beginning of Title until the Similar questions block pops up
  2. Scroll into this block
  3. Add something into the Title
  4. Scrolls again in the Similar questions block

Observed behavior

Text is super-imposed


Firefox 81.0.1 (64bits)
MacOS 10.15.6
External display (IIYAMA 24", 1980x1080px)

I do not have any issue using Chrome 85.0.4183.121 (64bits)

  • firefox 82.0+build2-0ubuntu0.20.04.1 in ubuntu focal also present.
    – nobody
    Commented Oct 29, 2020 at 7:54

I can see this issue on Firefox 85.0.2 (64-bit) on OS: Windows 10 Enterprise.

  1. Start typing question title.
  2. Wait for "Similar question" list to load.
  3. Start scrolling.
  4. enter image description here

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