If you go to the about:profiles page on Firefox, do you see more than one profile listed?

It's possible that Firefox has two profiles on it: one that it's using when you open Firefox regularly and another that it's using when you open a link on another program. That could explain why the layout is different.

If you do see more than one listed, make note of what profile is the one you are using when you normally open Firefox. The next time you open a link from an external program, go to the about:profiles page again and set the default profile to the one that you use for your regular browsing.

Hopefully that works for you.

Hi Wesley,

Thanks for your suggestion. Firefox is using my default profile when the issue occurs - please see attached screen grab.

Perhaps these observations might trigger some thoughts:

1. If I open FF first and then click on links in external applications, the web pages open as new tabs in the existing window with the header bar showing. 2. If FF is not open and I click on links in external applications two things happen - a new empty FF window with header bar visible opens in the background and a new foreground windows open at the page link with no header bar visible.

Any other ideas?

Many thanks,

John

Could it be this bug ?

• Bug 1603956 - macOS Catalina: Menu labels missing when cold opening Firefox from link or other app

Yes, many thanks for pointing me to this post, Guess I'll have to wait for future updates to fix.