The lock screen is the first thing that is displayed on your Mac when you start to use it. So many users want to have a customized lock screen on their devices. Basically, there is already an initial background set on your Max, but if you want to put there your own one, keep on reading.

How to replace lock screen on your Mac

Actually, the lock screen it’s a blurry version of your wallpaper. For those who want to change it, there is a simple way to do that. Firs that you should know before doing that is:

• The photo must be in .png or .heic file format, depending on your macOS version
• The photo should fit the resolution of your screen. Otherwise, you’ll see tons of pixels

How to add your lock screen wallpaper

If you want to add your lock screen wallpaper, you should follow the steps which would be mentioned in the section below:

1. First of all, you should hold Ctrl + Click on your desired login screen photo, then, you should click on Open With, and tap on Preview app.
2. After that, you should head to the top toolbar. There, you should tap on the File tab and click o Save As.
3. Then, you should save it somewhere on your Mac.
4. Next, you should press the Command (⌘) + Shift + G keyboard combination. In this way, you will let the Go To Folder menu be opened.
5. After that, you should Copy and Paste /Library/Caches in the address bar, next, you should tap on  Go.
6. Then, you should copy the new image that has been saved as “com.apple.desktop.admin.png” and then, you should paste it to the /Library/Caches folder.
7. You can use the Command (⌘) + C key combination to copy and the Command (⌘) + V combination to paste or just pull and drop the picture. 
8. After you have completed the process, you can log out from your Mac and enjoy your new login background picture.

How to change the lock screen picture on a MacBook Air

If you want to change the lock screen on MacBook Air, you should follow the prompts which would be mentioned in the section below:

• First of all, you should open the Photos app and find your desired picture.

• After that, you should do a right-click on the picture and click on the Set Desktop Picture option which would be displayed in the drop-down menu.

If you want to customize your Mac lock screen without changing the desktop background, you should:

• Open the desired picture in Preview.

• Do a double-click on the picture name at the top of the screen and give it a new name “lockscreen.png”.

• Head to Finder, then to Go, and click on Go to Folder.
• Fill in the path /Library/Caches/Desktop Pictures and tap on Go.
• Click on the folder that contains the “lockscreen.png” file.
• Pull and drop the desired picture into the folder.
• Tap on Replace in the window that would be displayed.

How to change the lock screen on macOS Sierra

If you want to change the lock screen on macOS Sierra, you should follow the prompts which would be mentioned in the section below:

1. First of all, you should open System Preferences.
2. After that, you should click on Desktop & Screen Saver.
3. After you have completed the steps above, you should head to the left window pane to select the photo you want to have as your new background

How to change the lock screen on macOS Mojave

If you want to change the lock screen on macOS Mojave, you should follow the instructions which would be mentioned in the section below:

1. First of all, you should press Ctrl + Click on the image that you want to have as the login screen photo, then, you should tap on Open With, and click on Preview app.
2. After that, you should head to the top toolbar. There, you should tap on the File tab and click on Save As.
3. Then, you should select HEIC as the necessary file format and name it Mojave.heic.
4. Next, you should save it on your Mac.
5. After that, you should open Finder and head to /Library/Desktop Pictures.
6. Then, it would be required to paste the lock screen that you want to have.
7. Next, you will be asked to confirm the procedure by entering the admin password.
8. After you have completed the prompts above, you will have a new lock screen set.

How to change the lock screen on macOS Catalina

If you want to change the lock screen on macOS Catalina, you should follow the steps which would be mentioned in the section below:

1. First of all, it’s required to convert your image to JPG.
2. After that, you should rename your picture as Catalina and save it in the Downloads folder.
3. Then, you should restart your Mac and press Command (⌘) + R to start the recovery mode.
4. Next, you should head to the top menu and tap on Utilities. Then, you should open the Terminal app.
5. After that, you should fill in cp /Volumes/MacHD\ -\ Data/Users/[your user name]/Downloads/[Catalina].jpg /Volumes/MacHD/System/Library/Desktop\ Pictures/Catalina.heic
6. Then, you should reboot your Mac.
7. Next, you should change any option in Preferences > Users & Groups > Login Options.
8. After you have completed the instructions above, you can view your new lock screen.

All in all, there is nothing complicated if you want to change your lock screen.