I'm using Ubuntu 17.10 with GNOME shell and Numix-Circle icon theme.

When I hover over the Numix icon for Nightly Web Browser, which is pinned to the dock I get the title "Nightly Web Browser".

enter image description here

But when I launch the program, another icon pops up at the bottom, with the name "Nightly".

enter image description here


You need to add a proper StartupWMClass line to the .desktop launcher corresponding to the application (refer to this). Follow these steps:

  1. Open Files and go to your /usr/share/applications folder. Look for the "Nightly" file (i.e. the launcher for the application you want to fix) and copy it.
  2. Paste the file in ~/.local/share/applications. It should look like a file with the name <filename>.desktop.
  3. Right click on this .desktop file and open with Text Editor.
  4. Launch "Nightly" (i.e. the application you want to fix) from "Activities".
  5. Run xprop WM_CLASS in Terminal.
  6. Place the cursor over the opened "Nightly" window. The cursor should turn into a crosshair already. Click. You should get a WM_CLASS string for "Nightly" in Terminal.
  7. In the .desktop file opened in Text Editor add the following line


    In place of OBTAINED-VALUE put a value you got from step 6 without any quotes.

  8. Save the .desktop file.
  • 2
    I am trying to do the same with PyCharm. Got "sun-awt-X11-XFramePeer", "jetbrains-pycharm-ce" as the output for step 6. I used StartupWMClass=jetbrains-pycharm-ce and it works.
    – d4nyll
    Jan 11 '18 at 15:59
  • 7
    9. Rename .desktop file to OBTAINED-VALUE.desktop (e.g. jetbrains-phpstorm.desktop instead phpstorm.desktop), works in Ubuntu 18.04 Jul 12 '18 at 16:29
  • 3
    Thank you for the answer. It would be really nice to have an explanation of what happens. I don't want to blindly follow some instructions. What is going on and what does the fix do? Would be great if someone could help out.
    – marts
    Jan 26 '19 at 12:03
  • 3
    @marts Please go through this for an explanations: askubuntu.com/questions/367396/…
    – pomsky
    Jan 26 '19 at 12:05
  • 3
    @AlekseyDeryagin In step 6, I got WM_CLASS: not found. As the misbehaving application was kile and the name of the file org.kde.kile.desktop, I just added the line StartupWMClass=kile and it works. My wild guess is that the last full-stop separated part of the filename (right before .desktop) should match the StartupWMClass value.
    – Ansa211
    Feb 11 '19 at 12:57

related to :

Kile icon buggy in left (launcher) bar (ubuntu 18.04)

On ubuntu 18.04

  • open the file : org.kde.kile.desktop
  • at : /usr/share/applications
  • add this line at the end of file : StartupWMClass=kile
  • press ALT+F2, r

It works for me


Ubuntu 20.04 on Wayland

  1. Press Alt + F2
  2. Type "lg" and hit Enter (Looking Glass)
  3. Click on the "Windows" tab.
  4. You should see the titles of all your windows. Below each one you will find a wmclass property. Write down or copy the value you see.
  5. Open up the .desktop config file corresponding to your application. It should be in the ~/.local/share/applications/ folder.
  6. On a new line add wmclass=VALUE_FROM_ABOVE

In my case for Firefox it was "Firefox Developer Edition" and I had to add the line below to my .desktop file:

wmclass=Firefox Developer Edition

In my case, I followed @Chris Hayes, method of finding the WMClass and update the file, see below for an example. I referred other *.desktop files in /usr/share/applications and found that Ubuntu 20.04 is using "StartupWMClass" as the variable and NOT "WMClass". I could not find the Icon for this application so I had to download from the internet a jpeg file icon from Google Image search, save it in the path and assign to the variable "Icon". Please note, I believe this field "StartupWMClass" is case sensitive

[Desktop Entry]
Comment=View pdf documents
Exec=/opt/pdfstudioviewer2020/pdfstudioviewer2020 %F
StartupWMClass=PDF Studio Viewer

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