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

Why does Firefox always start up windowed instead of in fullscreen?

  • 8 replies
  • 1 has this problem
  • 3 views
  • Last reply by ottomotor

more options

My installation of Firefox always starts up in windowed mode, even though I only ever use it in fullscreen. I thought that it might have been that I enabled privacy.resistFingerprinting, but that wasn't it. I also tried refreshing and then reinstalling Firefox, and that didn't work either. Could it maybe be some other setting that I might not even remember having changed? Or is my Sync account just broken?

My installation of Firefox always starts up in windowed mode, even though I only ever use it in fullscreen. I thought that it might have been that I enabled privacy.resistFingerprinting, but that wasn't it. I also tried refreshing and then reinstalling Firefox, and that didn't work either. Could it maybe be some other setting that I might not even remember having changed? Or is my Sync account just broken?

All Replies (8)

more options

https://support.mozilla.org/en-US/kb/changes-toolbars-and-window-sizes-are-not-saved You may have corrupt xulstore.json file.

Close Firefox. Open your file browser to this hidden location:

  • Mac: *~/Library/Application Support/Firefox/Profiles
  • Linux: *~/.mozilla/firefox/Profiles
  • Windows: %AppData%\Mozilla\Firefox\Profiles
  • *C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\Profiles
  • Windows XP: C:\Documents and Settings\<user>\Application Data
    \Mozilla\Firefox\Profiles\

Search for the above files. Then rename or delete them. Restart Firefox.

more options

Alright, that worked, thanks! Because of how that article was phrased, I thought that refreshing Firefox also created a new profile, but apparently not. Should have read it more closely I guess :D

more options

Glad to help. Safe Surfing.

more options

Okay, just now I started Firefox and it opened up windowed again, and this time, deleting xulstore.json doesn't work. Do I have to refresh Firefox now? And do you know how xulstore.json becomes corrupted?

more options

https://support.mozilla.org/en-US/kb/update-firefox-latest-version?cache=no Did you update Firefox to the latest version 66.0.4 May 5, 2019 Fixes add-on certificate issue.

more options

Yes, I just checked and then deleted the file again (in case the update had just happened) and the issue is still there :|

more options
more options

Well, after resetting / deleting / whatever my profile, reinstalling Firefox etc, I figured that my Firefox Sync account might have had something to do with it, since it always works for a while after I do one of the above, and at some point it randomly starts going windowed again. I have now done a reinstall without syncing with my previous Sync account, and so far it's worked. Let's see if it stays that way.