Use an old iMac as the main display for a MacBook.
Keep the MacBook as your main computer and reuse the larger iMac screen as its primary display. DeskJoin Screen creates an extended display over your local connection—without a hardware dongle, product account, or matching Apple ID.
Video tutorial
MacBook on the desk. iMac as the main display.
Watch the complete setup, then follow the written steps below.
Can an iMac be the main monitor for a MacBook?
Yes. The MacBook remains the computer running your apps, files, and work, while the iMac displays the MacBook's main desktop. DeskJoin Screen creates an additional macOS display on the MacBook and streams that display to the iMac over the local network.
Start the connection with the MacBook open. Once its extended desktop appears on the iMac, close the powered MacBook. Its built-in display turns off, leaving the iMac as the screen you use for the MacBook.
Step-by-step setup
How to use an old iMac as a monitor for a MacBook
Step 1
Check both Macs and connect power
The MacBook and iMac must both run macOS 12.3 or later. Connect the MacBook to its power adapter, and connect an external keyboard and mouse or trackpad to the MacBook before using it with the lid closed.
Step 2
Install DeskJoin Screen
Download and open DeskJoin Screen on both the MacBook and the iMac. No product account or matching Apple ID is required.
Step 3
Connect the two Macs
Place both Macs on the same Wi-Fi or Ethernet network. For a direct wired Mac-to-Mac connection, configure Thunderbolt Bridge in macOS.
Step 4
Start Extend from the MacBook
On the MacBook, open DeskJoin Screen, choose Extend, and select the iMac. The MacBook creates an additional display and sends it to the iMac.
Step 5
Close the MacBook lid
After the extended desktop appears on the iMac, close the MacBook lid. With the MacBook connected to power, the built-in display turns off and the iMac becomes the screen you work on.
Step 6
Work with an external keyboard and mouse
The MacBook stays awake after you close the lid. Use the external keyboard and mouse or trackpad connected to the MacBook while viewing and working on its desktop through the iMac.
DeskJoin Screen takes a different approach. The iMac continues running macOS and receives a software display stream from the MacBook. It does not turn the iMac panel into an HDMI, USB-C, Mini DisplayPort, or Thunderbolt video input.
Choose a clear, comfortable resolution
Once connected, open Displays settings on the MacBook and select a scaled resolution that keeps text comfortable on the iMac. A very high workspace resolution can make menus and text look too small even when the image itself is sharp.
For the most consistent motion, use Ethernet or Thunderbolt Bridge when practical. A strong local Wi-Fi connection also works well. DeskJoin Screen is designed to provide a second display that looks clear and feels smooth for everyday windows, documents, browsing, and video.
Using an iMac as a MacBook monitor: FAQ
Can I use an old iMac as the main monitor for a MacBook?
Yes, if both Macs can run macOS 12.3 or later. Connect the MacBook to power, start an Extend session, confirm that the desktop appears on the iMac, and then close the MacBook lid.
Can I use an iMac as a monitor for a MacBook Pro or MacBook Air?
Yes. DeskJoin Screen works with compatible MacBook Pro and MacBook Air models running macOS 12.3 or later, provided the iMac also meets the software requirement.
Does DeskJoin Screen use Target Display Mode?
No. DeskJoin Screen is a software-based local display connection. It does not use the iMac's HDMI or DisplayPort input and does not depend on Apple's discontinued Target Display Mode workflow.
Does every old iMac work as a MacBook monitor?
No. The iMac must still boot normally and run macOS 12.3 or later. Very old iMac models that cannot run the required macOS version are not supported.
Do both Macs need the same Apple ID?
No. DeskJoin Screen does not require a matching Apple ID, product account, subscription, or cloud login.
Can I connect the MacBook and iMac with a cable?
Yes. You can use Ethernet or a direct Thunderbolt connection configured with Thunderbolt Bridge. You can also connect over the same Wi-Fi network.
