Fulling theming macOS Big Sur

Introduction

Everyone with a jailbroken has probably already themed their iPhone, right ?
Well, actually, you don’t even need to be jailbroken to enjoy alternative icons on iOS, but theming has been a long tradition in the jailbreak community.

Felicity Pro and Dotto+ on iPhone 11

So, why not doing the same on macOS ?
Well, mostly because, just like iOS, it’s not possible on stock. While you can indeed change thrid-party apps icons easily, more advanced theming (like system apps icons or notification badges) cannot be customized on stock.

In this article, I’m going to describe the different techniques one can use to achieve full theming on macOS Big Sur. This may work as well on Monterey (and Ventura ?) but I haven’t tested it yet.
Here is a little preview of what we will be achieving :

Where to get icons for macOS ?

If you don’t want to make custom icons yourself, you can visit macosicons.com. They have thousands of incredible icons and you’ll most probably find one you like.
If you can’t find what you’re looking for, you’ll have to make icons yourself. To edit a picture online, you can use lunapic.com to edit images, then turn them into .icns files using Image2icon available for free on the Mac AppStore.

Disabling SIP and SSV

To achieve our goals, we have to disable SIP (System Integrity Protection) and SSV (Signed System Volume). These are system protections built in macOS and disabling them may alter your system security and leave your Mac more vulnerable to malware.

Please do NOT do this is you don’t know what you’re doing !
I’m not responsible for any problem that may result from doing this.

Boot into Recovery Mode, open the terminal and run :\

csrutil disable
csrutil authenticated-root disable

Then reboot to macOS.
If your Mac fails to boot (there is no real reason this can happen if you didn’t mess anything, but that happened to me once), just reinstall macOS. You won’t lose your data if you don’t erase your main disk. As usual, having a backup is the safest way to prevent data loss (which can always happen…).
Also note that enabling verbose boot can help diagnosing issues during boot if you encounter any.

Once in macOS, check if everything is disabled correctly :
run csrutil status, you should see it’s disabled.
Same, run csrutil authenticated-root status, it should be disabled too.

Changing third-party apps icons

Editing third-party apps icons does NOT require SIP and/or SSV to be disabled, so you can keep them on if you’re just planning to theme third party apps.

Go to Finder -> Applications and select the app you want to theme.
Then, you can either press Command + I or go right-click -> Get Info.
Finally, drag and drop your new icon into the icon slot : Drop here
This is trivial and has already been discussed countless times online, so I won’t go into any further details here.

Changing System apps icons

This is normally not possible because the System volume is mounted as read-only. Unfortunately, it’s not possible to remount it directly as read-write (it used to be possible on Catalina and earlier) and to do it, it’s necessary to disable SIP and SSV, as we did earlier.

Which volume should we mount ?

Open Disk Utility and look for Macintosh HD. Note down the device identifier (here, it is /dev/disk3s1).

It’s normal if you don’t have the “System snapshot mounted” message. It appears for me because I’ve already done all the steps described further down the article.

Then, create a mountpoint :

mkdir /tmp/mount

and finally, mount your disk here

sudo mount -w -t apfs /your/identifier /tmp/mount

Editing the icons

Then we can navigate to /tmp/mount/System/Applications/ where System apps are stored. Now, this location is readable and writable.
You may now change any icon you want using the method decsribed earlier for third party apps (using drag and drop).

Then, I strongly recommend you test your edits by performing the steps described below in the section “Saving changes”.

Modifying notification badges

Do you seriously find these red notification badges pretty ? Sorry, but that’s ugly

I’m ususally a huge fan of “stock” visuals, but these huge red dots look really ugly, especially if you’ve opted, like me, for a certain color scheme. These badges can look horrible.
So, let’s change them ! More precisely, we’re gonna change the badges color.

With your System volume mounted as read-write (see the “Changing System apps icons” section above on how to achieve this), navigate to /tmp/mount/System/Library/CoreServices/Dock.app/Contents/Resources.
Once you’re there, find 2 files called statuslabel.png and statuslabel@2.png.

Just backup them and replace them with custom icons (make sure to keep the same resolution and the exact same filename).

Save your changes (see section below), reboot and you’ll see nice badges with the color that suits best to your theme : There is a badge on the Reminders app

Modifying the Finder icon

Same as before, mount your System volume as read-write and navigate to /tmp/mount/System/Library/CoreServices/Dock.app/Contents/Resources.
Then, just replace finder.png and finder@2.png by yours. Again, don’t forget to backup the original files, save your changes and reboot.

Modiying the calendar icon

Because yes, there is a big quirck with the Calendar app : its icon is generated at runtime, because it changes every day…
Trying any of the above methods will not work (you can try yourself, but I already did it for you…).

You could force the system to use a static icon (editing the Calendar app’s Info.plist) but the icon won’t change over time, which is not satisfying.

So, we have to understand how the Calendar app changes its icon. Reversing the executable in Hopper was useless, same when reversing its Docktile plugin (/System/Applications/Calendar.app/Contents/Resources/Calendar.docktileplugin).

Searching online suggests the existence of an App-empty.icns file that we could replace to achieve what we want.
However, while this has already been discussed here, this file can longer be found where we expect it to be.
Fortunately, the terminal can help us, and running sudo find / -name "App-empty.icns" shows interesting results :

Let’s navigate to this path, but using our read-write permissions to be able to edit the file !
So, we’ll go /tmp/mount/System/Library/PrivateFrameworks/CalendarUIKit.framework/Versions/A/Resources/

Once there, you can backup and replace the App-empty.icns file ! Once again, save your changes and reboot. The calendar icon will have changed. Cool, isn’t it ?

Saving changes

We now have to make a new snapshot with your last changes and tell the system to use this snapshot to boot.
Skipping this step will result in all your changes being lost.

sudo bless --folder /tmp/mount/System/Library/CoreServices --bootefi --create-snapshot

Then, we have to flush the icon cache, and force the system to regenerate a new one.

sudo rm -rfv /Library/Caches/com.apple.iconservices.store > /dev/null 2>&1
sudo find /private/var/folders/ -name com.apple.dock.iconcache -exec rm -rf {} \; > /dev/null 2>&1
sudo find /private/var/folders/ -name com.apple.iconservices -exec rm -rf {} \; > /dev/null 2>&1

Finally, unmount the disk

sudo umount -f /tmp/mount

and reboot !

You should see your changes saved and in action !
Congratulations ! 🎉