How can I start a separate instance (not profile) of Chromium, with its own icon?

I was inspired by the other answers, but I discovered that we only need to set --class and --user-data-dir options for Chrome's executable.

So I wrote a script to make this automatically and if you want to try (don't worry, it won't perform any action before you confirm -- unless you use --force), just run:

bash -c "$(curl -fsSL "https://raw.githubusercontent.com/felipecassiors/dotfiles/master/scripts/create_alternative_chrome_shortcut.sh")"

If you want to know more about it, take a look here.

The only caveat is that since it uses --user-data-dir instead of --profile-directory, the new Chrome instance will act like a fresh new. This is needed because of this bug.

In the end, you'll end up with something like this:

Check GIF here.

The WMClass seems to have no authority when it comes to Chromium... I came up with this abomination (personal opinion... I'd just like for it to work with sh :) ) It has a few tricks, but is pretty robust for two windows.. The script sets individual classes for the opened chromium windows (not profiles, even though that is what I am after) You could specify further windows too, but they have to be manually added by adding more "specificprofile1" along with the corresponding function.. Maybe someone could make it have more.. logic!

#!/bin/bash
# chromium-start.sh $1 
# e.g. put: 
# chrome-start.sh "Profile 1" to .desktop Exec=
# wmctrl -o 1366,0 ; chromium-browser %U --profile-directory=Profile 2 & sleep 3; wmctrl -o 0,0

# $1 = Profile folder name

profilename=$1

#2nd Chromium profile
specificprofile1="Profile 1"

echo "starting Chromium"
echo "args: " $1
echo "Profile name: " $profilename
echo "Specific profile: " $specificprofile1

# Just setting Chromium scaling variable, because of course Google Devs don't care about no fractional scaling on linux
scale_var=0.8

# Check if Chromium window with the specified class already exists
# Also allows using icons as "taskbar" switches (clicking icon takes to corresponding Chromium Window)
if wmctrl -l -x | grep "chromium-$profilename"
then
echo "Chromium Window exists, moving focus to it"
wmctrl -x -R chromium-"$profilename"
echo "true"

# Check if 2nd profile $specifiedprofile1 has been started yet or not. The WMCLASS(es) has to have been set correctly...
elif [[ "$specificprofile1" == "$profilename" ]] && [[ ! "`wmctrl -l -x | grep chromium-"$specificprofile1"`" ]]
then
    # TODO: Nesting
    if [ "$specificprofile1" == "$profilename" ]
    then
    echo $specificprofile1 "equals" $profilename
    fi
echo "#2 Chromium Window for $specificprofile1 does not exist"
# wmctrl moves to specific position of desktop (1366 means moving to the following workspace since my resolution is 1366x768)
# Be careful if using sleep timing, since the command needs to have enough time to execute to have the window in the correct workspace
wmctrl -o 1366,0
chromium-browser  --profile-directory="$profilename" --force-device-scale-factor=$scale_var %U &
# https://askubuntu.com/a/626524/654028
# Set's the chromium window which was opened latest to have a custom class, since Chromium doesn't care about the --class= flag...
# It has it's limitations, but should be robust enough for most use... Has not been tested long term.. Something probably could reset the WM_CLASS again
# xprop -id "$(wmctrl -l -x| grep "chromium-browser" | tail -n 1 |awk '{ print $1 }')" -f WM_CLASS 8s -set WM_CLASS "chromium-browser.chromium-$specificprofile1"

# Alternative method for checking if a window with specified class exists
# xprop -id "$(wmctrl -l -x| grep "chromium-$profilename" | tail -n 1 |awk '{ print $1 }')" | grep -o "WM_CLASS(STRING) = ".*"" | grep -o '".*"' | tr -d '"'

# https://stackoverflow.com/a/19441380/5776626
winrep=""
while [[ ! "`echo $winrep | grep -l "Map State: IsViewable"`" ]]
do
    winid="$(wmctrl -l -x| grep "chromium-$profilename" | tail -n 1 |awk '{ print $1 }')"
    # print $winid
    winrep="$(xwininfo -id $winid | grep -o 'Map State: IsViewable')"
    # print $winrep
    sleep 0.75
    xprop -id "$(wmctrl -l -x| grep "chromium-browser" | tail -n 1 |awk '{ print $1 }')" -f WM_CLASS 8s -set WM_CLASS "chromium-browser.chromium-$specificprofile1"
done
# sleep 3

# Move Window directly to workspace (#2 with 1366x768 resolution x = 1366), optionally comment out wmctrl -o 1366,0
# wmctrl -v -i -r $winid -e 0,1366,0,-1,-1

# sleep 5
# Move back to workspace #1
wmctrl -o 0,0


elif ! wmctrl -l -x | grep chromium-"$profilename"
then
echo "#3 Chromium Window $profilename does not exist"
wmctrl -o 0,0
chromium-browser  --profile-directory="$profilename" --force-device-scale-factor=$scale_var %U &


# https://askubuntu.com/a/626524/654028
# ....
# sleep 3

winrep=""
while [[ ! "`echo $winrep | grep -l "Map State: IsViewable"`" ]]
do
    winid="$(wmctrl -l -x| grep "chromium-$profilename" | tail -n 1 |awk '{ print $1 }')"
    # print $winid
    winrep="$(xwininfo -id $winid | grep -o 'Map State: IsViewable')"
    # print $winrep
    sleep 0.75
    xprop -id "$(wmctrl -l -x| grep "chromium-browser" | tail -n 1 |awk '{ print $1 }')" -f WM_CLASS 8s -set WM_CLASS "chromium-browser.chromium-$profilename"
done
wmctrl -o 0,0
# xprop -id "$(wmctrl -l -x| grep "chromium-browser" | tail -n 1 |awk '{ print $1 }')" -f WM_CLASS 8s -set WM_CLASS "chromium-browser.chromium-$profilename"
fi

Issues:

Printing gives errors (deprecation warnings..):

Unescaped left brace in regex is deprecated, passed through in regex; marked by <-- HERE in m/%{ <-- HERE (.*?)}/ at /usr/bin/print line 528.

For debugging you can use the following to print out the errors when using actual icons: https://askubuntu.com/a/664272/654028 (# The Manual alternative)

awk '/^Exec=/ {sub("^Exec=", ""); gsub(" ?%[cDdFfikmNnUuv]", ""); exit system($0)}' chrome-ws2.desktop

while loop bugs out, probably because of looping interval

Error: no such file "at while function"
xwininfo: error: -id requires argument
xprop: error: Invalid window id format: .
xwininfo: error: -id requires argument
xprop: error: Invalid window id format: .
xwininfo: error: -id requires argument
xprop: error: Invalid window id format: .

Also when clicking a corresponding .desktop icon too fast (before the custom class has been set ?), a new window will be opened..

(quite) Sometimes when starting from both Chromium too fast (~<3s), the class of the previously opened window gets reset to chromium-browser.chromium-browser.. Then you can expect the icons to have swapped around or other unexpected behavior.

What worked (cobbled together from the various answers and comments - thanks!) was to create a .desktop file in ~/.local/share/applications with a few tweaks:

[Desktop Entry]
Version=1.0
Name=Chromium Browser 2
GenericName=Web Browser 2
Comment=Chromium Alternate
Exec=/usr/lib/chromium-browser/chromium-browser --user-data-dir=/home/dandv/Chr2 --class="Chr2"
Terminal=false
X-MultipleArgs=false
Type=Application
Icon=/home/dandv/chromium-browser-2.png
Categories=Network;WebBrowser;
MimeType=text/html;text/xml;application/xhtml_xml;x-scheme-handler/http;x-scheme-handler/https;
StartupNotify=true
Actions=NewWindow;Incognito;TempProfile;
X-AppInstall-Package=chromium-browser
StartupWMClass=Chr2

Make sure to replace /home/dandv/ with your home directory. Using ~ did not work.

The tweaks I applied to the .desktop file were:

1. Add --class="SomethingLikeChr2" to the Exec= line
2. Add StartupWMClass=SomethingLikeChr2 to the [Desktop Entry] (use the same unique value as above; apparently this is what makes a separate window, that won't get lumped in with existing Chromium windows
3. Add --user-data-dir=... to the Exec line, due to this Chromium bug.

Result

The easiest way I know of is using the More Tools -> Create Shortcut. From there it will create a .desktop entry that you can customize the icon and you can go to chrome://apps to modify settings like opening as a window.