I'm using a conference application called Zoom. There are URLs that can be clicked to open the application and let jump in right away to the meeting that ID existed in the URL. For example: https://zoom.us/j/1234567890 But none of the URLs I tried actually opens the application. Or for instance when I try to login to my account, the app opens Firefox which after logging in through the web, redirects me to zoommtg://zoom.us/google?code=XXX and Firefox shows a message saying "The address wasn’t understood". I tried the following boolean key on the about:config page for Firefox: network.protocol-handler.expose.zoommtg=false And I tried assigning true instead of false, but this didn't do the trick. My Firefox has the following key/value network.protocol-handler.expose-all;true I understand that this configuration makes me not need to set the previous one as it overrides it. From within my ~/.local/share/applications $ cat Zoom.desktop [Desktop Entry] Name=Zoom Comment=Zoom Video Conference Exec=/usr/bin/zoom %U Icon=Zoom.png Terminal=false Type=Application Encoding=UTF-8 Categories=Network;Application; StartupWMClass=zoom MimeType=x-scheme-handler/zoommtg;application/x-zoom; X-KDE-Protocols=zoommtg Name[en_US]=Zoom $ cat mimeapps.list [Default Applications] text/html=firefox_firefox.desktop x-scheme-handler/http=firefox_firefox.desktop x-scheme-handler/https=firefox_firefox.desktop x-scheme-handler/about=firefox_firefox.desktop x-scheme-handler/unknown=firefox_firefox.desktop x-scheme-handler/zoommtg=Zoom.desktop application/x-zoom=Zoom.desktop How can I configure Firefox to redirect the Zoom URLs to the application, so I can login to my account and use meeting links to join the meetings instantly ? I uploaded a screenshot to show that Zoom doesn't show in Firefox's Applications list, but I'm not sure it isn't showing up !