Firefox Community Forum

"The bookmarks and history system will not be functional because one of Firefox's files is in use by another application. Some security software can caused this problem".

How do I resolve this problem?

When File Explorer of Windows 11 25H2 tries to access and open an icon-file in the FF (144-64bit) profile's 'shortcutcache' folder, explorer gets Access Denied. The account running Firefox has admin rights.

Looking to the ACL of the profile folder containing the folder 'shortcutcache' show no reason for the blocking. Trying this with a new profile did not help.

Hi. According to my observations, only Mozilla Firefox and Adobe Reader have this problem so far.

Windows 11 + Multi-Monitoring Windows 10 have this Bug not !

Open Firefox, drag the window to the second or third monitor, and suddenly there is another hidden Firefox window on the taskbar of that display. If you move Firefox back to the main monitor, it disappears again. Or you can close Firefox and restart it on the desired monitor.

This is an annoying little bug, and I don't understand why Microsoft or Mozilla haven't fixed it yet. It's easy to reproduce and has obviously been around for a while. Since it only affects the two programs mentioned above so far, an MS update will probably not fix it; instead, the developers at Mozilla and Adobe need to address it.

Here the Same Topic in Adobe Forum. No bug fix to date

https://community.adobe.com/t5/acrobat-discussions/taskbar-phantom-window-when-using-multiple-monitors/td-p/14390169

I hope you release a bug fix soon... but since that hasn't happened yet, I'm afraid it will take a while... I'm surprised, because I'm sure many people are experiencing this annoying problem, and in my opinion it's not a big challenge for your developers.

@Mozilla Please Fix this Bug. I know Windows 11 is not better than Windows 10 but Supports End and many Users and Customers used in Future this OS and if you don't want to lose any more market share, it's important to fix this minor bug for ordinary users too. Thanks ;-)

For some reason text rendered in canvases (used by Minecraft hostings to display console) is distorted. I'm not getting this behavior in other browsers (including Zen – Firefox fork). The issue persists in both stable and nightly versions, with and without hardware acceleration, in safe mode too. Any clues?

Firefox recently sent out its monthly newsletter (Oct '25) with all sorts of options that can be enabled on Firefox. I'm a computer illiterate & foolishly chose some of the options -- don't remember which nor know how to discover them.

Now javascript is no longer enabled on my MacBook Air (macOs Big Sur 11.7.10). I cannot access my protonmail account and many many other sites.

I've gone cross-eyed accessing "fixes" that are labelled "only for advanced users" & am bright enough to not even try.

Is there a simple fix (short of wiping my computer -- with data going back 11 years) that even I can do?

If you have "fixing your firefox for Dummies" then please email me with a solution. [edited email from public community support forum]

I must have done something to mess this up,can someone help me fix this, cannot bookmark. I have used Firfox for many years. Thank you. Joe Daraio email- [edited email from public community support forum]

Hi Can you please help i have tried everything to get rid of this message i have uninstalled and reinstalled i have constantly refreshed and nothing helps,I get the message The bookmarks and history system will not be functional because one of firefoxs files is in use by another application also for quick access place your bookmarks here on the bookmark toolbar. I am not very technical but it is driving me mad please fix this for me Thanks

My Windows11 taskbar has an icon for firefox. If i left click on it (or just hovers) it shows thumbnail preview of the open windows. If to many it turns into a vertical list with the window names.

Lately (couple of months), when two or more firefox tabs or windows are open, I get a vertical list with those open windows but beneath it a complete list of empty entries (even more than there are processes in the task manager ...).

When I restart Windows it goes away for a while. But sometimes returns, I feel it is related to Windows updates as I have the feeling it started with a Windows update, went away with an update and is now back with an update. But that is just a feeling.

I attach an image with that empty list.

Very annoying to deprive me of my preferred news source. Firefox refuses to load any link on Netflix

   Here is the message "The page you are trying to view cannot be shown because the authenticity of the received data could not be verified.
   Please contact the website owners to inform them of this problem."

Please fix this or advise Thank you. David Vosbein [edited email and phone# from public community support forum]

THIS IS MADDENING AND I WANT IT TO STOP. i AM SAY FOR EXAMPLE FACEBOOK AND I AM SCROLLING ORIGINALLY I HAVE THE PAGE SET AT 90 AS I SCROLL IT HAS GONE AS FA DOWN AS 50 WHY WILL IT NOT STAY WHAT IS GOING ON AND WHY IT IT KEEPS DOING THIS I WILL GO TO GOOGLE CHROME AND NOT GO BACK TO FIREFOX THERE IS NO REASON IT SHOULD BE JUMPING LIKE THAT AND DO NOT TELL ME IT IS AD OS BECAUSE I TURNED THEM OFF AND IT STILL DID IT RIGHT NO AS I AM TYPING THIS I STARTED AT 100 AND NOW IT IS 50 AND AS I SCROLL HERE IT CONTINUES TO GO LOWER AS I MOVE THIS PAGE THE NUBER KEEPS DROPPING WHY??

I am experiencing significant performance problems in Mozilla Firefox when using certain AI-powered tools. Below are the specific issues:

   Flux AI & Diagramming AI Performance Warnings

       Issue: When accessing Flux AI or Diagramming AI tools, Firefox displays a warning message stating, "This site is slowing down Firefox."

       Observed Behavior:

           Delayed response times or freezing when interacting with these tools.

           High CPU usage (observed via Task Manager) when the tools are active.

       Expected Behavior: Smooth operation without performance degradation, as seen in other browsers (e.g., Chrome or Edge).

   CMS Sign-Out Failure

       Issue: Unable to sign out of my Content Management System (CMS). The action either freezes or refreshes without logging me out.

       Troubleshooting Attempted: Cleared cache/cookies, disabled extensions, tested in Safe Mode—issue persists.

   ChatGPT Menu Error

       Issue: Clicking the three-dots (⋮) menu in ChatGPT triggers an error instead of displaying options.

       Error Context: Mentions "Flux AI," suggesting a possible conflict or integration failure.

Since the last Firefox update, I am unable to sign into my Outlook account. When I click "Sign In" it opens a new tab with the sign-in buttons. Works fine in Edge and Chrome.