Can You Use a MacBook as a Monitor? The Definitive Guide

Unfortunately, directly using a modern MacBook as an external display for another device is not officially supported by Apple. While the allure of repurposing that gorgeous Retina display is strong, current macOS versions lack native features for “target display mode” – the bygone era feature that allowed older iMacs to function as monitors. So, a simple plug-and-play solution? Sadly, no.

Delving Deeper: Why the Limitation?

Apple’s design philosophy has shifted. The modern MacBook is a powerhouse of performance and portability, not a passive display device. The hardware and software are primarily optimized for output, not input, making it less efficient to handle display signals from external sources.

The Ghost of Target Display Mode

For those long-time Apple aficionados, the mention of Target Display Mode (TDM) evokes fond memories. This feature, available on older iMacs, allowed them to act as external displays via Thunderbolt or Mini DisplayPort. However, TDM was quietly retired, leaving users searching for alternatives.

Modern Alternatives: Clumsy Workarounds and Third-Party Apps

While a direct “plug-and-play” solution is unavailable, several workarounds allow you to approximate the functionality, albeit with caveats.

Workaround 1: Screen Sharing – A Software Solution

Screen Sharing, a built-in macOS feature, allows you to control one Mac from another over a network. This can be used to effectively see the screen of one Mac on another, but it’s not a true monitor replacement.

How to Enable Screen Sharing

1. On the MacBook you want to use as the monitor (the “host” Mac): Go to System Preferences > Sharing.
2. Check the Screen Sharing box.
3. Note the VNC address displayed.
4. On the MacBook you want to display the content (the “client” Mac): Open Finder, press Cmd+K to open the “Connect to Server” window.
5. Enter the VNC address you noted earlier, and click Connect.

Limitations of Screen Sharing

• Performance: Screen sharing relies on network connectivity, so expect latency and potentially lag, especially with graphically intensive tasks or over Wi-Fi.
• Control: You’re essentially remotely controlling the “host” MacBook, not just using its display. This means you need to manage two separate operating systems.
• Not a True External Monitor: You cannot simply drag windows from the “client” Mac onto the “host” Mac’s screen as you would with a real external display.

Workaround 2: Third-Party Apps – The Promise (and Peril)

Several third-party apps claim to offer functionality similar to Target Display Mode. These apps often use network protocols or specialized drivers to stream the display from one device to another.

Popular Apps for Screen Streaming

• Duet Display: A popular option that uses a wired connection (USB) for potentially lower latency. Primarily designed for using iPads as external displays, but can also work between Macs.
• Luna Display: A hardware dongle coupled with software, offering a more robust solution with lower latency compared to pure software-based approaches. However, Luna Display is designed to use iPads as a secondary display, not other Macs.
• Spacedesk: A free option that allows you to use a Windows PC as a secondary display for another device. While not directly applicable to using a MacBook as a monitor, it demonstrates the technical possibilities.

Cautions When Using Third-Party Apps

• Compatibility: Ensure the app is compatible with both macOS versions running on your MacBooks.
• Security: Exercise caution when installing third-party apps, especially those requiring system-level access. Research the app’s reputation and developer before installing.
• Performance: Performance can vary significantly depending on the app, network conditions, and the hardware capabilities of your MacBooks.

The Ultimate Solution: Just Buy a Monitor

Let’s be honest: if you need a dedicated external monitor, the simplest and most reliable solution is to purchase one. Modern displays offer superior image quality, connectivity, and dedicated functionality that workarounds simply cannot replicate.

Benefits of a Dedicated External Monitor

• Plug-and-Play Simplicity: Connect via HDMI, DisplayPort, or Thunderbolt, and you’re good to go.
• Superior Image Quality: Modern monitors offer high resolutions, accurate color reproduction, and fast refresh rates.
• Ergonomics: Proper monitor placement is crucial for comfortable and productive work.
• Dedicated Functionality: Features like built-in USB hubs, adjustable stands, and specialized display modes enhance your workflow.

Frequently Asked Questions (FAQs)

Here are 12 frequently asked questions to address your concerns comprehensively.

1. Will Target Display Mode ever return to modern MacBooks?

Highly unlikely. Apple’s focus is on individual device performance and seamless integration within its ecosystem, not on repurposing devices as passive displays.

2. Can I use an iPad as a monitor for my MacBook?

Yes, using apps like Duet Display or Luna Display. These apps are specifically designed for using iPads as secondary displays for Macs.

3. Is using Screen Sharing safe?

Screen Sharing uses encrypted connections, making it reasonably safe on trusted networks. However, always use strong passwords and be cautious when using it on public Wi-Fi.

4. What is VNC, and how does it relate to Screen Sharing?

VNC (Virtual Network Computing) is a protocol that allows you to remotely control one computer from another. Screen Sharing in macOS uses VNC under the hood.

5. Will using a MacBook as a monitor drain its battery quickly?

Yes, especially when using Screen Sharing or third-party apps. The MacBook will be actively processing and displaying the screen, consuming significant power.

6. Can I use a USB-C to HDMI adapter to make my MacBook a monitor?

No. USB-C to HDMI adapters are designed for outputting video from the MacBook to an external display, not for inputting video into the MacBook.

7. Does the MacBook Pro M3 have any hidden features to enable monitor functionality?

No. The M3 MacBook Pro, like its predecessors, does not have any hidden or undocumented features for using it as a monitor.

8. What’s the best way to minimize latency when using Screen Sharing?

Use a wired Ethernet connection instead of Wi-Fi. Close unnecessary applications on both MacBooks to free up resources.

9. Are there any hardware modifications I can do to enable Target Display Mode?

No. Attempting hardware modifications is highly discouraged and will likely void your warranty. It is unlikely to be successful.

10. Can I use AirPlay to mirror my iPad’s screen to my MacBook?

AirPlay is designed for outputting video from a device (like an iPad) to a compatible display (like an Apple TV or AirPlay-enabled TV). It cannot be used to input video into a MacBook.

11. What are the minimum system requirements for using Screen Sharing effectively?

Both MacBooks should be running relatively recent versions of macOS (ideally, the same version). A fast network connection is also essential.

12. Are there any open-source alternatives to Duet Display or Luna Display?

While there aren’t direct open-source equivalents with the same level of polish and performance, projects like barrier (formerly Synergy) offer keyboard and mouse sharing across multiple computers, which can be helpful in a multi-device setup, although it doesn’t directly address the screen sharing aspect.

Conclusion: Embrace the Dedicated Display

While the idea of using a MacBook as a monitor is tempting, the available workarounds come with significant limitations. Save yourself the hassle and invest in a dedicated external display. You’ll enjoy a superior experience, improved productivity, and avoid potential performance issues on your beloved MacBook. In the long run, your eyes (and your workflow) will thank you.