We're calling on all EU-based Mozillians with iOS or iPadOS devices to help us monitor Apple’s new browser choice screens. Join the effort to hold Big Tech to account!

This site will have limited functionality while we undergo maintenance to improve your experience. If an article doesn't solve your issue and you want to ask a question, we have our support community waiting to help you at @FirefoxSupport on Twitter and/r/firefox on Reddit.

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

How do you prevent Firefox from creating the Parent.lock file, a file that ALWAYS prevents Firefox from loading the next time I start up my PC?

  • 1 reply
  • 1 has this problem
  • 1 view
  • Last reply by cor-el

more options

OS: Windows 7 Home Premium (64-bit)

Ever since I have updated to version 38.0.1, I cannot run Firefox on my PC unless I do a bunch of things prior to previously shutting down my PC. Those things are the following:

1) Close / kill Firefox 2) Delete "Parent.lock" file

It appears Firefox always creates the Parent.lock file on my PC when I open the browser. If I do not delete this file before shutting down my PC, then the next time I start up my PC, I cannot start Firefox because there is a task called "firefox.exe" already running on my PC. This task cannot be killed -- I have tried a number of programs. Once I am here, I also can no longer delete the "parent.lock" file because the "firefox.exe" task is using it.

Please let me know if there is a solution.

Thanks.

OS: Windows 7 Home Premium (64-bit) Ever since I have updated to version 38.0.1, I cannot run Firefox on my PC unless I do a bunch of things prior to previously shutting down my PC. Those things are the following: 1) Close / kill Firefox 2) Delete "Parent.lock" file It appears Firefox always creates the Parent.lock file on my PC when I open the browser. If I do not delete this file before shutting down my PC, then the next time I start up my PC, I cannot start Firefox because there is a task called "firefox.exe" already running on my PC. This task cannot be killed -- I have tried a number of programs. Once I am here, I also can no longer delete the "parent.lock" file because the "firefox.exe" task is using it. Please let me know if there is a solution. Thanks.

All Replies (1)

more options

Firefox no longer removes the parent.lock file when you close Firefox. The time stamp of this file is used to check for startup issues and make it possible to offer to start in Safe Mode.

Are you closing Firefox before shutting down the computer?

You shouldn't let Windows close down Firefox, but close the application yourself (File > Exit or the power button in the "3-bar" Firefox menu button drop-down list).

Use "Firefox > Exit" (Windows: Firefox/File > Exit; Mac: Firefox > Quit Firefox; Linux: Firefox/File > Quit) to close Firefox if you are currently doing that by clicking the close X on the Firefox title bar.

See also: