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Firefox is constantly creating prefs-1.js files

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Ever since I upgraded to Firefox 60.5 ESR, it is now constantly creating prefs-1.js files in the profile directory. These files are created and then quickly deleted, but this is happening at a rate of at least one a second so the hard disk is constantly chattering. I tried downgrading to Firefox 60.4 ESR, but the problem has remained. At the moment, I am unable to use Firefox due to this constant high disk activity.

Ever since I upgraded to Firefox 60.5 ESR, it is now constantly creating prefs-1.js files in the profile directory. These files are created and then quickly deleted, but this is happening at a rate of at least one a second so the hard disk is constantly chattering. I tried downgrading to Firefox 60.4 ESR, but the problem has remained. At the moment, I am unable to use Firefox due to this constant high disk activity.

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  • User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E; wbx 1.0.0; rv:11.0) like Gecko

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cor-el
  • Top 10 Contributor
  • Moderator
17334 solutions 156717 answers

It is normal that Firefox first creates a temp file named prefs-1.js when there are changes made to prefs and a new prefs.js needs to be created. Firefox first creates a prefs-1.js temp file and once this has done properly prefs-1.js is renamed to prefs.js to replace the existing prefs.js file.

I don't know why Firefox wants to update prefs.js at the rate you reported.

Start Firefox in Safe Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration is is causing the problem.

  • switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Appearance
  • do NOT click the "Refresh Firefox" button on the Safe Mode start window
It is normal that Firefox first creates a temp file named prefs-1.js when there are changes made to prefs and a new prefs.js needs to be created. Firefox first creates a prefs-1.js temp file and once this has done properly prefs-1.js is renamed to prefs.js to replace the existing prefs.js file. I don't know why Firefox wants to update prefs.js at the rate you reported. Start Firefox in <u>Safe Mode</u> to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if <u>hardware acceleration</u> is is causing the problem. *switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Appearance *do NOT click the "Refresh Firefox" button on the Safe Mode start window *https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode *https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

Question owner

Thank you for the reply.

The prefs-1.js are not actually being renamed to prefs.js ... they are simply created and deleted in rapid fashion as the modification date stamp on prefs.js hasn't changed in many hours. Also, starting in Safe Mode does not change this behaviour. Finally, before receiving your reply, I had already tried Refreshing Firefox, but this also didn't make any difference.

For some reason Firefox believes an update of the prefs.js file is necessary, when in reality it isn't. I wonder if Firefox performs a "diff" between the two js files and then just deletes the temp one as it detects nothing has actually changed.

The only reason I have noticed this behaviour is because my PC has a traditional HDD rather than a SSD and the noise of the file write is constant. If you open up Resource Monitor (Disk tab) then the hundreds of file writes are easy to see.

Thanks.

Thank you for the reply. The prefs-1.js are not actually being renamed to prefs.js ... they are simply created and deleted in rapid fashion as the modification date stamp on prefs.js hasn't changed in many hours. Also, starting in Safe Mode does not change this behaviour. Finally, before receiving your reply, I had already tried Refreshing Firefox, but this also didn't make any difference. For some reason Firefox believes an update of the prefs.js file is necessary, when in reality it isn't. I wonder if Firefox performs a "diff" between the two js files and then just deletes the temp one as it detects nothing has actually changed. The only reason I have noticed this behaviour is because my PC has a traditional HDD rather than a SSD and the noise of the file write is constant. If you open up Resource Monitor (Disk tab) then the hundreds of file writes are easy to see. Thanks.

Question owner

This behaviour has now been observed on multiple company PCs and is certainly not an isolated occurrence impacting just a single PC. Furthermore, this behaviour is visible on both 60.5 ESR and 65.0. I see from a web search that this problem has occurred in the past, so is it possible that a recent code change has inadvertently reintroduced the previous problem. Please note that our users are now abandoning Firefox in favour of Chrome to prevent possible excessive wear on both HDDs and SSDs.

Thanks.

This behaviour has now been observed on multiple company PCs and is certainly not an isolated occurrence impacting just a single PC. Furthermore, this behaviour is visible on both 60.5 ESR and 65.0. I see from a web search that this problem has occurred in the past, so is it possible that a recent code change has inadvertently reintroduced the previous problem. Please note that our users are now abandoning Firefox in favour of Chrome to prevent possible excessive wear on both HDDs and SSDs. Thanks.