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Why do I have 3 black squiggles in top corners of browser window

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  • 1 has this problem
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  • آخر ردّ كتبه cor-el

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I have noticed I now have 3 squiggly black lines in the top corners of all the grey frames to windows I open in Firefox. They do not appear in Safari or Opera. Why is this?

I have noticed I now have 3 squiggly black lines in the top corners of all the grey frames to windows I open in Firefox. They do not appear in Safari or Opera. Why is this?

الحل المُختار

The Reset Firefox feature can fix many issues by restoring Firefox to its factory default state while saving your essential information. Note: This will cause you to lose any Extensions, Open websites, and some Preferences.

To Reset Firefox do the following:

  1. Go to Firefox > Help > Troubleshooting Information.
  2. Click the "Reset Firefox" button.
  3. Firefox will close and reset. After Firefox is done, it will show a window with the information that is imported. Click Finish.
  4. Firefox will open with all factory defaults applied.


Further information can be found in the Refresh Firefox - reset add-ons and settings article.

Did this fix your problems? Please report back to us!

Read this answer in context 👍 2

All Replies (3)

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الحل المُختار

The Reset Firefox feature can fix many issues by restoring Firefox to its factory default state while saving your essential information. Note: This will cause you to lose any Extensions, Open websites, and some Preferences.

To Reset Firefox do the following:

  1. Go to Firefox > Help > Troubleshooting Information.
  2. Click the "Reset Firefox" button.
  3. Firefox will close and reset. After Firefox is done, it will show a window with the information that is imported. Click Finish.
  4. Firefox will open with all factory defaults applied.


Further information can be found in the Refresh Firefox - reset add-ons and settings article.

Did this fix your problems? Please report back to us!

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Thanks Tylerdowner - squiggles gone!

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See also this thread for a screenshot:


I would assume that it is caused by an extension if a new profile helped.

Start Firefox in Safe Mode to check if one of the extensions or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance/Themes).