Customizing Spotify notifications on Linux

I recently wanted to customize Spotify media notfications on Linux. Every time I change songs, I get a desktop notification with the new song’s information. I wanted to this notification to stand out in comparision with other notfications on my system: a notification from Spotify should be outlined in green. This was a quick and fun project which utilized a lot of Linux knowledge that I’ve built up over the years, and I thought I’d share the process.

Notifications on Linux work through D-Bus, a message bus that allows applications to communicate with each other. Applications can publish messages to the message bus, and other applications can read those messages. Protocols ensure there is a standard structure and order for messages. For example, here is the protocol for notifications, which I needed to reference for this project.

Spotify sends messages to D-Bus, but which application reads them? That’s where notification daemons come in. There are many available options for notfication daemons - i3 users often use dunst.

I happen to use mako, but they’re all similar. Whenever a notification is published on D-Bus, mako reads it and shows a small window with the notfication content. It provides a simple config file for customizing this window (font, size, location, color, etc).

The path is clear: I need to configure mako to change the border color for notifications published by Spotify.

Reading the manual

First, I need to know how to configure mako based on information in the notification.

man mako redirects me to the config file documentation on man page 5. With man 5 mako, I can see that I can configure notifications based a variety of fields.

•   app-name (string)
•   app-icon (string)
•   summary (string): exact match on the summary of the notification. This field conflicts with summary~.
•   summary~ (string): a POSIX extended regular expression match on the summary of the notification. This field conflicts with summary.
•   body (string): an exact match on the body of the notification. This field conflicts with body~.
•   body~ (string): a POSIX extended regular expression match on the body of the notification. This field conflicts with body.
•   urgency (one of "low", "normal", "critical")
•   category (string)
•   desktop-entry (string)
•   actionable (boolean)
•   expiring (boolean)
•   mode (string): only apply style options in this section if the provided mode is currently enabled. For more information about modes, see the MODES section.

Based their provided example and the options provided in the rest of the file, I should be able to do this:

[app-name="Google Chrome"]
border-color=#ffbf00
background-color=#000000

This would change the border and background color notifications coming in from Google Chrome. There’s a lot of flexibility here. For notifications coming from Spotify, I could even match an artist name or song title with a regex for more fine-grained configuration. My favorite artist could be shown in another color, for example.

To do any of this, I’ll need to figure out what information Spotify is pubishing on the message bus. In this case, I want to match the app name. It looks like the string needs to be exact match, so rather than guessing, I want to confirm exactly what name Spotify is using when publishing notifications.

Eavesdropping on inter-process messages

I can monitor D-Bus messages using dbus-monitor. This should allow me to directly inspect the message and see what data Spotify is publishing to the bus, and what mako should be picking up.

dbus-monitor is a bit too chatty to read easily, however. I’ll need to narrow down the messages to just the ones I care about. After reading the output to figure out how it’s broken down and playing with some filters, I ended up with the following command:

dbus-monitor "interface='org.freedesktop.Notifications'" | grep "member=Notify" -A 10

This narrows down the output to “Notify” messages as specified by this documentation.

When changing a song in Spotify, I can see the message:

method call time=1739299183.583906 sender=:1.1008 -> destination=:1.1242 serial=1015 path=/org/freedesktop/Notifications; interface=org.freedesktop.Notifications; member=Notify
   string "Spotify"
   uint32 62
   string ""
   string "Chasing the Torrents"
   string "Yu-Peng Chen - Genshin Impact - Jade Moon Upon a Sea of Clouds (Original Game Soundtrack)"
   array [
   ]
   array [
      dict entry(
         string "icon_data"

Based on this output, it seems like the first field is the app name (“Spotify”), the fourth is the song title, and the fifth is the album title. Matching up the fields with the above documentation, we get

For the curious, it’s this track:

Fantastic - I’ve confirmed that “Spotify” is the correct app name, and have more information on where to find the artist, song, and album data in the future.

Putting it together

Using this information, I can finish configuring mako. I’ve matched Spotify’s branding colors using https://usbrandcolors.com/spotify-colors/.

[app-name=Spotify]
border-color=#1DB954
background-color=#191414

Success! The end result that only Spotify notifications have a green border. In the image, this is shown next to a regular notification, generated with notify-send "Test" "This is a test notification".

Why?

Seems like a lot of work for a green border. Was it worth it?

I would say so. I enjoy feeling like I have full control over my computer - feeling like I can get it to do anything I want it to. Every time I learn more about how Linux works, it composes well with my existing knowledge. New avenues open up.

For example, with the information I have now, it’d be trivial to write a script that health checks one of my production environments, runs periodically with cron, and pops up an attention-grabbing red notification if anything is abnormal. Not bad!

I have other information in my mako config as well. If you’d like to replicate the same look, this is my full config.

font=IBM Plex Sans 12
width=300
height=100
margin=12
padding=12
border-size=2
border-radius=8
text-alignment=left

layer=overlay
anchor=top-right

markup=1
actions=1
history=1
icons=1
max-icon-size=48
icon-location=left

ignore-timeout=0
default-timeout=10000
max-history=100
max-visible=5
sort=-time

on-button-left=dismiss
on-button-middle=none
on-button-right=dismiss-all
on-touch=dismiss

background-color=#191414
text-color=#d9e0ee
border-color=#313244
progress-color=over #89b4fa

[urgency=low]
border-color=#313244
default-timeout=2000

[urgency=normal]
border-color=#313244
default-timeout=5000

[urgency=high]
border-color=#f38ba8
text-color=#f38ba8
default-timeout=0

[app-name=Spotify]
# https://usbrandcolors.com/spotify-colors/
border-color=#1DB954
background-color=#191414