Why Firefox keep creating prefs.js files?
It all starts after I updated Firefox to a new version with new design. For about 8 hours FIrefox creating at least from 600 to 800 prefs-*.js. After about a week or so, it creates 5k+ of those files! My corporate antivirus has a realtime file scanning and it can`t keep up with that amount of .js files, because Firefox creating about 10-15 files in a minute when I`m browsing! Because of that continuous scanning my laptop slows down. And after 7+k of prefs-*.js time of Firefox launch getting close to couple of minutes and it starts to work really fucking slow!! Especially when I watch some online videos. None of the browsers which I use, created so many junk. I`ve opened 10 of those prefs-*.js and they are roughly the same. Only differences is web addresses.. But I`m don`t visit a 600+ web sites in a day!! WTF? As a temporary solution I`ve created a .bat file to clean that mess. But this is only temporary! At home I`m using Chrome and i had thoughts to start using FIrefox.. But now I`m definitely will not use Firefox a home. I couldn`t work properly in the office, at home I want just use browser and not writing tons of scripts to make browser work as intended. Who knows what surprises will be waiting for me at future.. So can you help me to stop Firefox creating mess, because it`s the only browser IT security are allowed to use at my company.
P.S. While I was writing all this, Firefox created 73 prefs-*.js because i`ve switched two tabs dozen of times.. P.P.S I`m using Firefox 58.0 (64-bit)
Chosen solution
Firefox first creates a numbered temp file (prefs-##.js in this case) as a safety precaution and when creating file has finished without errors then the numbered temp file is renamed to the main file without the number (prefs.js). Only when the latter (renaming) fails you will see the numbered file stay and that is what is happening in your case. I assume that your security software immediately tries to scan the file while Firefox is working with it and that prevents Firefox from renaming the file because other software has a handle on it. It is normally best to exclude the Firefox profile folder in security software from scanning to avoid just these issues.
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Chosen Solution
Firefox first creates a numbered temp file (prefs-##.js in this case) as a safety precaution and when creating file has finished without errors then the numbered temp file is renamed to the main file without the number (prefs.js). Only when the latter (renaming) fails you will see the numbered file stay and that is what is happening in your case. I assume that your security software immediately tries to scan the file while Firefox is working with it and that prevents Firefox from renaming the file because other software has a handle on it. It is normally best to exclude the Firefox profile folder in security software from scanning to avoid just these issues.
Thanks for explanation!
Cor-el, Thanks for your explanation.
I have the same issue and use McAfee Internet Security. It does not allow excluding folders, or files with wildcards in the name, so I need to pick a file to exclude specifically.
Am I correct in excluding prefs.js to comply with your information above?
Hi relem
If you only have this issue with multiple prefs.js files then you can exclude this file. If there are more numbered files then exclude these as well.
cor-el said
Firefox first creates a numbered temp file (prefs-##.js in this case) as a safety precaution and when creating file has finished without errors then the numbered temp file is renamed to the main file without the number (prefs.js). Only when the latter (renaming) fails you will see the numbered file stay and that is what is happening in your case. I assume that your security software immediately tries to scan the file while Firefox is working with it and that prevents Firefox from renaming the file because other software has a handle on it. It is normally best to exclude the Firefox profile folder in security software from scanning to avoid just these issues.
Hi cor-el.
I've the very same problem as described above. The problem is that I cannot exclude the scan of the prefs files or the containing folder. And probably the AV software does exactly what you mentioned, preventing the renaming. Hence the thousands of prefs-xxxx files.
So, my question is: is it safe to get rid of all the prefs-xxxx files "manually" (i.e. delete them all)? Should I keep any of them for any reason? In other words, provided that I cannot avoid the creation, how to handle them? And... any chance this problem will be addressed in future releases?
Thank you.
You can remove all numbered prefs-## temp files because they serve no value. Only the real prefs.js matters and you may have to rename this file as well in case its date and time isn't current (i.e. there is a numbered file that is more recent). You can consider to rename the most recent numbered prefs-##.js file to prefs.js.