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Demystifying StartupWMClass
(thoughts.greyh.at)
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this post was submitted on 24 Jun 2026
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The desktop files are named
firefox.desktopandfirefox-nightly.desktop, both in/usr/share/applications.EDIT: For completeness, I also checked the window classes of the regular firefox:
It can be observed that it uses only the window class
firefox, but twice?Yeah in your case the best fix is probably REMOVING StartupWMClass from those launchers if it is present. Then it will only match the app id on the .desktop file name.
Hmm, but I thought the
StartupWMClassesin the desktop files are correct? I thought the issue is that firefox-nightly uses thefirefoxclass in addition to thefirefox-nightlyclassStartupWMClass is NOT needed if the .desktop file is named correctly.
I see, so I could remove it, but wouldn't I still see the same behavior, since firefox nightly apparently also uses the
firefoxwindow class?