When you turn your Mac on, do you notice the blurred image behind the login screen? By default it’s a blurred version of Sierra’s iconic wallpaper, or a blurred version of your current wallpaper.
Have you ever wished this image wasn’t blurred? Or that it was different than your default wallpaper? As it turns out, the user can control what shows up here, but it takes a few steps. Here’s how to configure this image to look exactly the way you want it to. This method works in macOS Sierra, Yosemite, and El Capitan.
The Easy Way: Change Your Desktop Wallpaper
If you use a single custom wallpaper on your Mac, you’re probably wondering why this article exists. That’s because changing the blurred image behind your login screen is as simple as changing your desktop wallpaper.
But there are some catches. For example: if your wallpaper is a rotating folder of images, macOS uses the default Sierra wallpaper instead. If you want to use one of your own images, you can do that, without ditching your rotating collection of images.
First, right-click your desktop, then click “Change Desktop Background.”
(Note: if you use multiple desktops in Mission Control, make sure that you open this window on your left-most desktop, labeled “Desktop 1.”)
Now change your wallpaper to whatever you’d like your login screen’s background to be.
If you want to switch back to the rotating folder you had before, you can do that, but first let’s make sure that macOS has set your new image as the background for your login screen. Open the finder, then choose Go > Go To Folder. Type
/Library/Caches and click Go.
In this folder, you should see an image here named “com.apple.desktop.admin.png,” and if your changes took hold this image will be a blurred version of whatever you set as your wallpaper. Sometimes this will take a minute, so be patient.
Once you see your image, go ahead and turn your rotating wallpaper back on, if you wish—in our tests this did not affect this file. Now log out of your account or restart your Mac to see your new login screen.
It’s working! Note that, if you have a rotating wallpaper, this change will not affect your lock screen, which will always show a version of your current wallpaper (on Desktop 1.) The login screen, however, is now set as a blurred version of your preferred image.
Use An Unblurred Picture For Your Login Screen
If you’d rather your login screen not be blurred, you can do that too! I recommend first following the steps above, so that there is an image in the /Library/Caches folder. Then, copy that image to your desktop by dragging it there.
We’ll use this image in a little bit. First, open whatever image you’d like to show up behind your login screen with Preview. Select the entire canvas (Command+A), then copy it (Command+C).
Next, head to your desktop and open the file you copied from /Library/Caches. Paste (Command+V) what you just copied.
You will need to move and resize what you’re pasting quite a bit in order to get everything just right. When you’re done, save the image (Command+S). Head back to your desktop, and drag your edited image to the /Library/Caches folder. You will be asked if you’d like to replace the file that’s there; click “Replace.”
You’ve now placed your custom background image. Go ahead and log out of your user account to see how it looks:
It worked! In my case, however, the white maple leaf is making it hard to read the white text used by macOS. To fix this, I found a different version of this image where the leaf is blue.
Much better! This version puts the darker part of the image behind the text, which makes it easier to read everything. You’ll probably have to experiment with this a little yourself, but to avoid problems favor dark images over light ones, and simple images over complex ones.
If you’re a Photoshop guru, you might prefer making an image yourself over messing around with Preview in this way. You can do that, but the image you create needs to meet specific criteria. It must be:
- A PNG file
- The same exact resolution as your primary display
- RGB, sRGB, or Adobe RGB color mode.
- 8bit colors
- Unlocked background layer
- Named “com.apple.desktop.admin.png”
In our tests, even doing all these things can still be hit-or-miss, so we suggest using the Preview method. It’s just simpler.
Add a Custom Message To Your Login Screen
You may have noticed, in the screenshots above, that I’ve left a custom message in my login screen. The idea is that if I lose my Mac, some good person may try to return it. It’s wishful thinking, perhaps, but it’s worth a shot.
If you’d like to leave your own such message, it’s easy! First, open System Preferences and head to Security & Privacy.
Make sure “Show a message when the screen is locked” is checked.
Next, click “Set Lock Message,” then enter whatever message you’d like.
I recommend leaving a phone number or email address. You could also mention a cash reward for returning the laptop, if you believe money enhances human kindness. It’s up to you.