Are you juggling multiple devices and wishing you could consolidate your screen real estate? Perhaps you have a powerful MacBook but also a desktop Mac that could benefit from a larger, more immersive display. Or maybe you’re looking for a cost-effective way to add a second monitor without shelling out for a new one. Whatever your reason, the good news is that your Mac can, in many cases, be used as a secondary monitor for another Mac. This article will delve deep into the various methods, requirements, and nuances of transforming your Apple laptop or desktop into a versatile external display. We’ll explore the official Apple solutions, third-party software options, and even some more unconventional approaches.
Understanding the Possibilities: Mac as a Monitor for Another Mac
The dream of using one Mac’s screen to extend or mirror the display of another Mac isn’t just wishful thinking. Apple, recognizing the growing need for flexible workflows, has provided built-in features to facilitate this. However, it’s crucial to understand the limitations and specific requirements for each method. We’ll break down the primary ways this can be achieved.
Leveraging Apple’s Built-In Solutions
Apple offers two primary, built-in methods to use your Mac as a display: Target Display Mode and Sidecar. Each has its own set of advantages, disadvantages, and compatibility requirements.
Target Display Mode: The Wired Solution
Target Display Mode is a feature that allows certain iMac models to be used as a display for another Mac. This is a wired solution, meaning it requires a physical cable connection. It’s a fantastic option if you have compatible hardware, offering a robust and low-latency connection.
What is Target Display Mode?
In essence, Target Display Mode turns your iMac into a monitor for another Mac. You connect your primary Mac (the source) to your iMac (the display) using specific cables, and then you trigger Target Display Mode on the iMac. The iMac then acts as a standard external display, receiving video input from the source Mac.
Compatibility Requirements for Target Display Mode:
This is where things get specific. Not all iMacs support Target Display Mode, and the supported models and connection types have evolved over the years.
- Source Mac (the one you want to display): Must be running macOS High Sierra (10.13.6) or earlier.
- Display Mac (the iMac you’re using as a monitor):
- 27-inch iMac (Late 2009) and 27-inch iMac (Mid 2010): Support Target Display Mode via Mini DisplayPort. These models require a Mini DisplayPort to Mini DisplayPort cable.
- iMac (Mid 2011) through iMac (Mid 2014): Support Target Display Mode via Thunderbolt. These models require a Thunderbolt to Thunderbolt cable.
- iMac (Retina 5K, 27-inch, Late 2014) and later: Do NOT support Target Display Mode. This is a significant limitation to be aware of.
How to Use Target Display Mode: A Step-by-Step Guide
1. Ensure Compatibility: Double-check that both your source Mac and your iMac meet the requirements outlined above.
2. Connect the Macs:
* For Mini DisplayPort Macs: Use a Mini DisplayPort to Mini DisplayPort cable to connect the two Macs.
* For Thunderbolt Macs: Use a Thunderbolt cable to connect the two Macs.
* Important Note: Make sure both Macs are powered on.
3. Put the iMac into Target Display Mode:
* On the iMac you want to use as a display, close all applications.
* Press Command + F2 on the iMac’s keyboard.
* The iMac’s screen should then switch to displaying the desktop of your source Mac.
4. Troubleshooting Target Display Mode:
* No Signal: Ensure you are using the correct cable type (Mini DisplayPort or Thunderbolt) and that it’s firmly connected. Try a different cable if possible.
* Wrong Resolution/Display Issues: Sometimes, restarting both Macs can resolve display issues.
* Keyboard Not Recognized: Ensure the keyboard connected to the iMac is a wired Apple keyboard. Wireless keyboards or third-party keyboards might not always be recognized for the Command + F2 shortcut.
* iMac Sleeping: If the iMac goes to sleep, you’ll need to wake it up and reactivate Target Display Mode.
Advantages of Target Display Mode:
* High Quality: Offers a crisp, high-resolution display with minimal lag, as it’s a direct hardware connection.
* No Software Installation: Relies solely on built-in macOS features.
* **Cost-Effective: Utilizes hardware you already own.
Disadvantages of Target Display Mode:
* Limited Compatibility: Only works with specific older iMac models.
* Requires Wired Connection: Limits placement flexibility.
* Source Mac OS Limitation: The source Mac needs to be running an older macOS version.
Sidecar: The Wireless and Wired Solution for iPads and Newer Macs
Sidecar is Apple’s modern solution that allows you to use your iPad as a secondary display for your Mac. While the primary focus is on iPads, it also opens doors for using newer Macs as displays through workarounds, though it’s not a direct feature. We’ll primarily focus on Sidecar as intended for iPads, but touch upon the broader implications.
What is Sidecar?
Sidecar extends your Mac’s desktop to your iPad wirelessly or via a USB connection. This allows you to use your iPad as a drawing tablet, a dedicated space for your tools, or simply to expand your workspace.
Compatibility Requirements for Sidecar (iPad as Display):
* Mac Requirements:
* MacBook Pro (2016 or later)
* MacBook Air (2018 or later)
* iMac (2015 or later)
* iMac Pro (2017 or later)
* Mac mini (2018 or later)
* Mac Pro (2019)
* Mac mini (2018) or later
* Must be running macOS Catalina (10.15) or later.
* iPad Requirements:
* iPad Pro (all models)
* iPad (6th generation) or later
* iPad mini (5th generation) or later
* iPad Air (3rd generation) or later
* Must be running iPadOS 13 or later.
* Connectivity:
* Both devices must be signed in to iCloud with the same Apple ID.
* Both devices must have Wi-Fi and Bluetooth turned on.
* Devices must be within about 10 meters (30 feet) of each other.
* For wired connection: USB-C to USB-C cable or USB-C to Lightning cable.
How to Use Sidecar (iPad as Display):
1. Ensure Compatibility: Verify both your Mac and iPad meet the requirements.
2. Sign in to iCloud: Make sure you are logged into the same Apple ID on both devices.
3. Enable Wi-Fi and Bluetooth: Ensure these are turned on for both devices.
4. Connect:
* Wirelessly: No action needed beyond the above.
* Wired: Connect your iPad to your Mac using a USB cable.
5. Initiate Sidecar:
* On your Mac, click the Control Center icon in the menu bar.
* Click “Display.”
* Under “Mirror or Extend,” select your iPad.
* Your iPad will now act as an extended display. You can choose to mirror or extend your Mac’s display.
Using a Mac as a Display with Sidecar (Workaround):
While Sidecar is designed for iPads, there are third-party applications that leverage the technology or similar screen-sharing protocols to enable using a Mac as an external display for another Mac. These are not official Apple solutions and often come with performance trade-offs. We’ll discuss these in more detail later.
Advantages of Sidecar:
* Flexibility: Works wirelessly or wired.
* Portability: Use your iPad on the go.
* Touch and Apple Pencil Support: Great for creative workflows.
* Modern Compatibility: Works with newer Macs.
Disadvantages of Sidecar:
* iPad Dependent: Primarily for use with iPads, not directly for Mac-to-Mac.
* Potential Lag: Wireless connections can sometimes introduce latency.
* Battery Usage: Can drain the iPad’s battery.
Third-Party Software Solutions: Bridging the Gap
When Apple’s built-in solutions don’t meet your needs due to compatibility or specific requirements, third-party software offers a viable alternative. These applications often use network protocols (like Wi-Fi or Ethernet) to stream your Mac’s display to another Mac.
Popular Screen Sharing and Remote Desktop Applications
Several applications are designed for screen sharing and remote access, and some can be adapted for use as an external monitor.
Air Display Connect and Air Display Host
Air Display is a well-known application that allows you to use an iPad or another computer as an external display for your Mac. They have historically offered solutions for Mac-to-Mac mirroring.
How Air Display Works:
Air Display typically involves installing a “host” application on the Mac you want to share the screen from and a “client” application on the Mac you want to use as the display. The two Macs then communicate over your local network.
Considerations for Air Display:
* Performance: Network-based solutions can introduce lag, especially over Wi-Fi. For smoother performance, a wired Ethernet connection between the two Macs is often recommended.
* Cost: These are typically paid applications, so budget for the software license.
* Setup: Requires installing software on both machines and configuring network settings.
Duet Display
Duet Display is another popular app, primarily known for its iPad mirroring capabilities, but it also offers Mac-to-Mac functionality.
How Duet Display Works:
Similar to Air Display, Duet Display requires installations on both Macs. It’s designed for a smooth experience, often prioritizing wired connections for optimal performance.
Considerations for Duet Display:
* Performance: Generally considered to have good performance, especially when using a wired connection.
* Subscription/One-time Purchase: Check their pricing model for Mac-to-Mac use.
* System Requirements: Always check the latest compatibility with your macOS versions.
Alternatives to Consider: ScreenRec, AnyDesk, TeamViewer
While not strictly designed as “monitor replacement” apps, tools like ScreenRec, AnyDesk, and TeamViewer offer robust screen sharing and remote control. If your primary goal is to access the desktop of another Mac and you don’t need the absolute lowest latency, these can be effective.
How They Work:
These applications establish a secure connection between two computers, allowing you to view and control the remote computer’s screen. You can configure them to run in a “view-only” mode, effectively using the remote Mac’s screen as a display.
Key Differences and When to Use Them:
* Focus: Their main purpose is remote access and support, not dual-monitor setups.
* Ease of Use: Often very straightforward to set up for remote viewing.
* Performance: Can be variable depending on network conditions and the app’s optimization for display streaming. They might not be ideal for tasks requiring precise mouse movements or fast-paced video.
Using an Older Mac as a Display for a Newer Mac
This is a common scenario. You might have a newer MacBook but an older, still functional iMac or Mac Pro that you’d like to repurpose as an external monitor.
The Challenge and Solutions
The primary challenge here is that newer Macs, particularly those running recent macOS versions, often lack the ports or specific hardware capabilities (like Mini DisplayPort or Thunderbolt for Target Display Mode) that older Macs supported for direct display input.
Network-Based Solutions are Key
For using a newer Mac as a display for an older Mac, network-based third-party software solutions are usually your best bet. As discussed above, applications like Air Display or Duet Display are designed to stream the display over your network.
Important Considerations for this Scenario:
- Wi-Fi vs. Ethernet: For the best experience, connecting both Macs via Ethernet cable to your router or directly to each other (if they have Ethernet ports) will significantly reduce latency and improve stability compared to Wi-Fi.
- Software Updates: Ensure you are using the latest versions of your chosen third-party software to benefit from performance improvements and bug fixes.
- MacBook Display Settings: On the Mac acting as the display, you’ll need to ensure its display settings are configured to extend or mirror the primary Mac’s desktop.
Can I Use a MacBook as a Monitor for Another MacBook?
Yes, this is also achievable using the same third-party software solutions mentioned previously. The principle remains the same: you’re streaming the display from one MacBook to another over your network.
Key Factors for MacBook-to-MacBook Mirroring:
- Network Speed: A fast and stable Wi-Fi connection (Wi-Fi 5 or Wi-Fi 6) is crucial. If both MacBooks have Ethernet ports (or you use USB-C to Ethernet adapters), this will provide the most reliable performance.
- Resource Usage: Running display streaming software can consume CPU and RAM on both machines. Ensure your MacBooks have sufficient resources to handle the added load without becoming sluggish.
- Display Resolution: Be mindful of the resolution you’re streaming. Streaming a very high-resolution display over a less-than-ideal network connection will likely result in poor performance.
Advanced Considerations and Alternatives
Beyond the primary methods, there are a few other things to consider, especially if your needs are more niche or if you’re facing specific hardware limitations.
Video Capture Cards (for Non-Mac Sources)
While this article focuses on Mac-to-Mac usage, it’s worth noting that if you wanted to use your Mac as a monitor for a different type of device (like a gaming console or a Windows PC), you would typically need a video capture card. These devices take an HDMI or other video input and make it accessible to your Mac’s software for viewing. This is a different use case but highlights the hardware requirement for direct video input.
Screen Mirroring vs. Display Extension
When using your Mac as a monitor, you’ll typically have two options:
- Mirror Display: Shows the exact same content on both screens. This is useful for presentations or when you want an exact replica of your primary display.
- Extend Display: Creates a larger, continuous desktop across both screens. This is ideal for multitasking, allowing you to have different applications open on each display.
The choice between these depends on your workflow and how you intend to use your secondary Mac display.
Performance Optimization
Regardless of the method you choose, optimizing performance is key to a satisfactory experience.
- Wired Connections: Always prioritize Ethernet over Wi-Fi when possible for stability and reduced latency.
- Close Unnecessary Applications: Free up system resources on both Macs by closing any applications you don’t need.
- Reduce Display Resolution: If you experience lag, try lowering the resolution of the extended display.
- Update Drivers and Software: Ensure all operating systems and any third-party applications are up-to-date.
When Direct Connection Isn’t Possible: The Network is Your Friend
The evolution of Apple’s hardware and software has meant that direct video input capabilities on Macs have become less common. Target Display Mode, while a fantastic feature, is largely retired. This makes network-based solutions the primary avenue for most users looking to use one Mac as a display for another, especially with newer hardware.
Conclusion: Reimagining Your Workspace
Using your Mac as an external monitor can be a powerful way to enhance productivity, declutter your workspace, and make the most of your existing Apple hardware. Whether you’re leveraging the direct hardware connection of Target Display Mode with compatible iMacs or opting for the flexibility of network-based third-party software, the ability to extend your digital canvas is within reach. By understanding the compatibility requirements and choosing the right solution for your specific setup, you can unlock a more versatile and efficient computing experience. Explore these options and transform your Mac into a valuable secondary display.
What is the primary benefit of using your Mac as an external monitor?
The main advantage of transforming your Mac into an external monitor is to significantly expand your screen real estate without needing to purchase a dedicated external display. This is particularly useful for users who frequently work with multiple applications, require more space for creative tasks like photo or video editing, or simply desire a more immersive viewing experience for their primary computer. It allows for better multitasking and improved productivity.
This capability also offers a cost-effective solution compared to buying a new monitor, especially if you already own a second Mac that isn’t being fully utilized. It leverages existing hardware, making it an environmentally friendly and economical choice. The convenience of having an additional display readily available without additional setup or clutter can be a major draw for many Mac users.
What are the different methods available to use a Mac as an external monitor?
There are two primary methods to achieve this functionality: AirPlay and third-party software solutions. AirPlay, specifically AirPlay to Mac, allows compatible Macs to receive content wirelessly from another Mac, iPhone, or iPad. This method is built into macOS and offers a convenient, cable-free experience for mirroring or extending your desktop.
Alternatively, dedicated third-party applications like Luna Display or Duet Display provide more robust and feature-rich solutions. These often offer a wired connection (USB or Thunderbolt) for lower latency and greater stability, as well as advanced features such as touch support and stylus integration. While these typically require a purchase, they generally offer a more professional and seamless experience for intensive use.
Are there any hardware requirements for using my Mac as an external monitor?
For AirPlay to Mac, the primary hardware requirement is that both Macs must be running compatible versions of macOS. Typically, the Mac acting as the display needs to be a MacBook Pro (2016 or later), MacBook Air (2018 or later), iMac (2015 or later), iMac Pro (2017 or later), Mac mini (2020 or later), or Mac Pro (2019 or later). Both Macs also need to be on the same Wi-Fi network and have Bluetooth enabled.
For third-party software solutions, the requirements can vary slightly depending on the specific application. However, generally, both Macs will need to be running relatively recent versions of macOS. Some solutions may also benefit from a wired connection, so ensuring your Macs have available USB-C or Thunderbolt ports can enhance performance and stability, though USB-A connections are often supported with adapters.
What is the performance like when using a Mac as an external monitor?
The performance can vary depending on the method used and network conditions. AirPlay to Mac generally provides a good experience for less demanding tasks like document editing or web browsing, offering a decent refresh rate and acceptable visual quality. However, for fast-paced content like gaming or video editing, you might notice some lag or a slight reduction in image clarity due to the wireless transmission.
Third-party software solutions, especially those utilizing a wired connection, typically offer superior performance with lower latency and higher resolutions. These are often designed to provide a near-native experience, making them more suitable for professional workflows where responsiveness and image fidelity are crucial. The stability of the connection is also generally more consistent with wired options.
Can I use my Mac as an external monitor for a Windows PC?
Using a Mac as an external monitor for a Windows PC is generally not possible directly through built-in macOS features like AirPlay. AirPlay is designed for Apple devices to connect to other Apple devices. However, some third-party software solutions are designed to bridge this gap and allow your Mac to function as a display for a Windows computer.
These cross-platform solutions often involve installing client software on the Windows PC and server software on the Mac, or vice versa, depending on the application. While these can work, the performance and usability can be more variable compared to Mac-to-Mac connections, and compatibility should be carefully checked for specific software.
What are the potential drawbacks or limitations of this setup?
One significant limitation can be the resolution and refresh rate limitations, especially when using wireless methods like AirPlay. While it works well for general productivity, it may not be ideal for high-refresh-rate gaming or color-critical design work. Another consideration is that the Mac used as a monitor will consume power and may run hotter, especially under sustained use.
Furthermore, the secondary Mac will have its own screen actively displaying content, which might impact its battery life if it’s a laptop and not plugged in. Depending on the software used, there might be licensing costs, and some solutions may require a constant internet connection or a local network connection, which could be a factor if you are working in environments with unreliable network access.
Is this setup suitable for professional creative work like video editing or graphic design?
For basic creative tasks such as light photo editing or organizing files, using a Mac as an external monitor can be perfectly adequate. The increased screen space can be beneficial for managing multiple windows and tools. However, for professional-grade video editing, high-end graphic design, or color-accurate work, the limitations of resolution, refresh rate, and potential latency might become apparent.
In these demanding scenarios, a dedicated, high-quality external monitor with a calibrated display, fast response times, and accurate color reproduction is generally recommended. While some advanced third-party solutions might come close, they may still not fully match the performance and reliability of a purpose-built display for mission-critical professional applications.