You can customize your login screen on your Mac. This article describes how you can change your macOS Big Sur login screen to display any image you want when your Mac turns on. Here is how:

The login screen is where you enter your password.
See also:
- macOS Catalina: How To Change The Login Screen Background
- How to Change the Login Screen Background on macOS Mojave
How to change the Big Sur login screen
1. On your Mac, in the Finder, choose Go > Go to Folder.

2. Type the following pathname and click Go.
/Library/Caches/Desktop Pictures

3. In this folder, you will see one or more folders. The folders are named after the name of the user’s UUIDs. Open this folder and you will see a file named “lockscreen.png”. Please note that if you do not have a folder named Desktop Pictures, create this folder inside the Caches folder. Then you will need to create a folder with UUID value as name inside the Desktop Pictures folder (see below).


Furthermore, If Desktop Pictures folder exists but if you do not see a folder inside the Desktop Pictures folder, you will again need to create one UUID value as name. Here is how.
See also: How To Screenshot (Print Screen) And Record Screen On Your Mac
A. On your Mac, open System Preferences and click Users & Groups.
B. Click the Lock icon and enter your passcode to unlock this section.
C. Right click (or control-click) on user name and select “Advanced Options…”.

D. Now, copy the UUID of your User-ID.
E. Now go to the “/Library/Caches/Desktop Pictures” folder again. And create a new folder. The name of this folder should be your UUID.
F. Now right click this new folder and click Get Info. Make sure that your computer has Write privileges. Grant permissions Read & Write to user, admin, everyone.
See also: Mac: How To Troubleshoot Screen Flickering
4. Now select the current lockscreen.png image (if you have this image in the folder) and rename it old-lockscreen.png.
5. Now find an image or photo that you want to use as your login screen background and drag-and-drop the image (name it lockscreen.png) into the open folder.

Now restart your Mac and you are done.
See also:
I am having the same problem as Becky, neither method works for me. I did go to my Macintosh HD/Library/Cache and found folder Desktop Pictures and made sure the new UUID folder held my new lockscreen.png image. When I restart, it is still on that nauseating multicolored image.
And suggestions would be so appreciated!
Lia- p.s. the existing Folder is not “locked”. The picture is my own picture which opens in the Start Page. There is no picture of the horrible Big Sur (red etc) within this folder. The tutorial shows a Folder which has the “forbidden” seal on it. I do not have this it seems. Thanks again.
Thank you ….however…..Macintosh HD/Library/Caches/Desktop Pictures (NOT the system library) contains a Folder with UUID and a subfolder lockscreen.png.
However, I did not manage to create a 2nd folder with my UUID. Does one need to import another picture in the already existing folder? Thanks for your answer. Best wishes, Lia
This method worked perfectly for me. The ridiculous pink irritant is gone!!!
Got it to work after realising there are 2 different Library folders on the mac. The one the article pointed to was wrong for me. But when you go to Macintosh HD/Library/Caches and create the Desktop Pictures folder in there, then follow the rest of the instructions, it works!
I hated the red/blue screen so much I wanted to throw up. Thanks so much for the article. Made my day when I saw my old Catalina calm island pic come up.
Hi, I can’t change it via the method in this article either, its driving me crazy. I tried to go to the folder you suggested but when I type it in all I get is a ping sound and it goes to Desktop-Local.
Did you create it in there? I’m really not sure why it won’t work and the bright colours on the log-in screen give me a headache 😛
Any help?
Thank you!
Tried creating a new desktop pictures directory in caches, then a new folder with UUID name, with new lockscreen.png. Made sure everyone could read & write. Still have the horrid red, yellow, blue art screen on restart.